diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5d87b0920..4da9e6ac7 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -36,8 +36,8 @@ jobs:
       - name: Run PHPUnit
         run: ./vendor/bin/phpunit
 
-      - name: Run Psalm
-        run: ./vendor/bin/psalm --show-info=false --threads=2
+      - name: Run PHPStan
+        run: ./vendor/bin/phpstan analyze --error-format=github
 
       - name: Run PhpCS
         run: ./vendor/bin/phpcs -n --parallel=2 --runtime-set ignore_warnings_on_exit 1
diff --git a/.idea/WooCommerce.iml b/.idea/WooCommerce.iml
index 692525fb1..3dddcc19e 100644
--- a/.idea/WooCommerce.iml
+++ b/.idea/WooCommerce.iml
@@ -73,6 +73,10 @@
       <excludeFolder url="file://$MODULE_DIR$/vendor/symfony/polyfill-php73" />
       <excludeFolder url="file://$MODULE_DIR$/vendor/inpsyde/composer-assets-compiler" />
       <excludeFolder url="file://$MODULE_DIR$/vendor/dhii/services" />
+      <excludeFolder url="file://$MODULE_DIR$/vendor/php-stubs/woocommerce-subscriptions-stubs" />
+      <excludeFolder url="file://$MODULE_DIR$/vendor/phpstan/extension-installer" />
+      <excludeFolder url="file://$MODULE_DIR$/vendor/phpstan/phpstan" />
+      <excludeFolder url="file://$MODULE_DIR$/vendor/szepeviktor/phpstan-wordpress" />
     </content>
     <orderEntry type="inheritedJdk" />
     <orderEntry type="sourceFolder" forTests="false" />
diff --git a/.idea/inspectionProfiles/Project_Default.xml b/.idea/inspectionProfiles/Project_Default.xml
index 0aea26527..d7a00f6ec 100644
--- a/.idea/inspectionProfiles/Project_Default.xml
+++ b/.idea/inspectionProfiles/Project_Default.xml
@@ -9,7 +9,8 @@
       <option name="CODING_STANDARD" value="Custom" />
       <option name="CUSTOM_RULESET_PATH" value="$PROJECT_DIR$/phpcs.xml.dist" />
     </inspection_tool>
-    <inspection_tool class="PsalmGlobal" enabled="true" level="ERROR" enabled_by_default="true" editorAttributes="ERRORS_ATTRIBUTES">
+    <inspection_tool class="PhpStanGlobal" enabled="true" level="WEAK WARNING" enabled_by_default="true" />
+    <inspection_tool class="PsalmGlobal" enabled="false" level="ERROR" enabled_by_default="true" editorAttributes="ERRORS_ATTRIBUTES">
       <scope name="WordPress Core" level="ERROR" enabled="false">
         <option name="showInfo" value="true" />
         <option name="findUnusedCode" value="true" />
diff --git a/.idea/php.xml b/.idea/php.xml
index ff26ece69..b41d83ce0 100644
--- a/.idea/php.xml
+++ b/.idea/php.xml
@@ -22,6 +22,7 @@
     <phpcsfixer_settings>
       <PhpCSFixerConfiguration standards="PSR1;PSR2;Symfony;DoctrineAnnotation;PHP70Migration;PHP71Migration" tool_path="$PROJECT_DIR$/vendor/bin/phpcbf" />
       <phpcs_fixer_by_interpreter interpreter_id="52b49461-5bc3-4708-8d5d-ae6e32b31b9c" standards="PSR1;PSR2;Symfony;DoctrineAnnotation;PHP70Migration;PHP71Migration" tool_path="/var/www/html/vendor/bin/phpcbf" timeout="30000" />
+      <phpcs_fixer_by_interpreter asDefaultInterpreter="true" interpreter_id="52b49461-5bc3-4708-8d5d-ae6e32b31b9c" standards="PSR1;PSR2;Symfony;DoctrineAnnotation;PHP70Migration;PHP71Migration" tool_path="/var/www/html/vendor/bin/phpcbf" timeout="30000" />
     </phpcsfixer_settings>
   </component>
   <component name="PhpCodeSniffer">
@@ -266,6 +267,7 @@
   <component name="PhpStan">
     <PhpStan_settings>
       <phpstan_by_interpreter asDefaultInterpreter="true" interpreter_id="29a5ef5c-f9cb-48bf-aa11-97d89c5f9549" timeout="60000" />
+      <PhpStanConfiguration tool_path="$PROJECT_DIR$/vendor/bin/phpstan" />
     </PhpStan_settings>
   </component>
   <component name="PhpStanOptionsConfiguration">
@@ -280,6 +282,7 @@
     <Psalm_settings>
       <PsalmConfiguration tool_path="$PROJECT_DIR$/vendor/bin/psalm" />
       <psalm_fixer_by_interpreter interpreter_id="29a5ef5c-f9cb-48bf-aa11-97d89c5f9549" tool_path="$PROJECT_DIR$/vendor/bin/psalm" timeout="60000" />
+      <psalm_fixer_by_interpreter asDefaultInterpreter="true" interpreter_id="52b49461-5bc3-4708-8d5d-ae6e32b31b9c" tool_path="/var/www/html/vendor/bin/psalm" timeout="60000" />
     </Psalm_settings>
   </component>
   <component name="PsalmOptionsConfiguration">
diff --git a/composer.json b/composer.json
index 953633362..11468cc07 100644
--- a/composer.json
+++ b/composer.json
@@ -35,9 +35,12 @@
     "inpsyde/php-coding-standards": "^1.0.0",
     "inpsyde/composer-assets-compiler": "^2.5",
     "php-stubs/wordpress-stubs": "^5.0@stable",
-    "php-stubs/woocommerce-stubs": "7.9.0",
+    "php-stubs/woocommerce-stubs": "^10.6",
     "vimeo/psalm": "^4.8 || ^5.13.0",
-    "vlucas/phpdotenv": "^5.6"
+    "vlucas/phpdotenv": "^5.6",
+    "szepeviktor/phpstan-wordpress": "^1.3",
+    "phpstan/extension-installer": "^1.4",
+    "php-stubs/woocommerce-subscriptions-stubs": "^8.4"
   },
   "autoload": {
     "psr-4": {
@@ -59,6 +62,8 @@
     "fix-coding-standards": "vendor/bin/phpcbf",
     "tests": "@php ./vendor/phpunit/phpunit/phpunit --coverage-text",
     "tests:no-cov": "@php ./vendor/phpunit/phpunit/phpunit --no-coverage",
+    "phpstan": "vendor/bin/phpstan analyse",
+    "phpstan:raw": "vendor/bin/phpstan analyse --no-progress --error-format=raw",
     "check-psalm": "vendor/bin/psalm",
     "check-psalm:no-cache": "vendor/bin/psalm --no-cache"
   },
@@ -98,7 +103,8 @@
       "composer/package-versions-deprecated": true,
       "automattic/jetpack-autoloader": false,
       "composer/installers": true,
-      "inpsyde/composer-assets-compiler": true
+      "inpsyde/composer-assets-compiler": true,
+      "phpstan/extension-installer": true
     }
   }
 }
diff --git a/composer.lock b/composer.lock
index 51d10fb41..55c3e3bf5 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "77e2348ec8a23178cb5e3847f3d89e13",
+    "content-hash": "ed3e20f78e98d09e3f91abbee50d6941",
     "packages": [
         {
             "name": "composer/ca-bundle",
@@ -2194,16 +2194,16 @@
         },
         {
             "name": "php-stubs/woocommerce-stubs",
-            "version": "v7.9.0",
+            "version": "v10.6.2",
             "source": {
                 "type": "git",
                 "url": "https://github.com/php-stubs/woocommerce-stubs.git",
-                "reference": "3a2f522e29451490c357af550227795d2b0fc55a"
+                "reference": "2cc4a2e110a4c6c93c2d4d06c786afa1faa2e9b8"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/php-stubs/woocommerce-stubs/zipball/3a2f522e29451490c357af550227795d2b0fc55a",
-                "reference": "3a2f522e29451490c357af550227795d2b0fc55a",
+                "url": "https://api.github.com/repos/php-stubs/woocommerce-stubs/zipball/2cc4a2e110a4c6c93c2d4d06c786afa1faa2e9b8",
+                "reference": "2cc4a2e110a4c6c93c2d4d06c786afa1faa2e9b8",
                 "shasum": ""
             },
             "require": {
@@ -2232,9 +2232,55 @@
             ],
             "support": {
                 "issues": "https://github.com/php-stubs/woocommerce-stubs/issues",
-                "source": "https://github.com/php-stubs/woocommerce-stubs/tree/v7.9.0"
+                "source": "https://github.com/php-stubs/woocommerce-stubs/tree/v10.6.2"
             },
-            "time": "2023-07-17T22:41:38+00:00"
+            "time": "2026-03-31T18:29:22+00:00"
+        },
+        {
+            "name": "php-stubs/woocommerce-subscriptions-stubs",
+            "version": "v8.4.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/php-stubs/woocommerce-subscriptions-stubs.git",
+                "reference": "6e225945956a40d711432a08a9f13d6cbad04922"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/php-stubs/woocommerce-subscriptions-stubs/zipball/6e225945956a40d711432a08a9f13d6cbad04922",
+                "reference": "6e225945956a40d711432a08a9f13d6cbad04922",
+                "shasum": ""
+            },
+            "require": {
+                "php-stubs/woocommerce-stubs": "^10.2",
+                "php-stubs/wordpress-stubs": "^5.3 || ^6.0"
+            },
+            "require-dev": {
+                "php": "~7.4 || ~8.1",
+                "php-stubs/generator": "^0.8.0"
+            },
+            "suggest": {
+                "symfony/polyfill-php74": "Symfony polyfill backporting some PHP 7.4+ features to lower PHP versions",
+                "szepeviktor/phpstan-wordpress": "WordPress extensions for PHPStan"
+            },
+            "type": "library",
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "description": "WooCommerce Subscriptions function and class declaration stubs for static analysis.",
+            "homepage": "https://github.com/php-stubs/woocommerce-subscriptions-stubs",
+            "keywords": [
+                "PHPStan",
+                "static analysis",
+                "subscription",
+                "woocommerce",
+                "wordpress"
+            ],
+            "support": {
+                "issues": "https://github.com/php-stubs/woocommerce-subscriptions-stubs/issues",
+                "source": "https://github.com/php-stubs/woocommerce-subscriptions-stubs/tree/v8.4.0"
+            },
+            "time": "2026-02-14T10:11:19+00:00"
         },
         {
             "name": "php-stubs/wordpress-stubs",
@@ -2595,6 +2641,54 @@
             ],
             "time": "2025-12-27T19:41:33+00:00"
         },
+        {
+            "name": "phpstan/extension-installer",
+            "version": "1.4.3",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/phpstan/extension-installer.git",
+                "reference": "85e90b3942d06b2326fba0403ec24fe912372936"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/phpstan/extension-installer/zipball/85e90b3942d06b2326fba0403ec24fe912372936",
+                "reference": "85e90b3942d06b2326fba0403ec24fe912372936",
+                "shasum": ""
+            },
+            "require": {
+                "composer-plugin-api": "^2.0",
+                "php": "^7.2 || ^8.0",
+                "phpstan/phpstan": "^1.9.0 || ^2.0"
+            },
+            "require-dev": {
+                "composer/composer": "^2.0",
+                "php-parallel-lint/php-parallel-lint": "^1.2.0",
+                "phpstan/phpstan-strict-rules": "^0.11 || ^0.12 || ^1.0"
+            },
+            "type": "composer-plugin",
+            "extra": {
+                "class": "PHPStan\\ExtensionInstaller\\Plugin"
+            },
+            "autoload": {
+                "psr-4": {
+                    "PHPStan\\ExtensionInstaller\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "description": "Composer plugin for automatic installation of PHPStan extensions",
+            "keywords": [
+                "dev",
+                "static analysis"
+            ],
+            "support": {
+                "issues": "https://github.com/phpstan/extension-installer/issues",
+                "source": "https://github.com/phpstan/extension-installer/tree/1.4.3"
+            },
+            "time": "2024-09-04T20:21:43+00:00"
+        },
         {
             "name": "phpstan/phpdoc-parser",
             "version": "2.3.2",
@@ -2642,6 +2736,59 @@
             },
             "time": "2026-01-25T14:56:51+00:00"
         },
+        {
+            "name": "phpstan/phpstan",
+            "version": "1.12.33",
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/phpstan/phpstan/zipball/37982d6fc7cbb746dda7773530cda557cdf119e1",
+                "reference": "37982d6fc7cbb746dda7773530cda557cdf119e1",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^7.2|^8.0"
+            },
+            "conflict": {
+                "phpstan/phpstan-shim": "*"
+            },
+            "bin": [
+                "phpstan",
+                "phpstan.phar"
+            ],
+            "type": "library",
+            "autoload": {
+                "files": [
+                    "bootstrap.php"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "description": "PHPStan - PHP Static Analysis Tool",
+            "keywords": [
+                "dev",
+                "static analysis"
+            ],
+            "support": {
+                "docs": "https://phpstan.org/user-guide/getting-started",
+                "forum": "https://github.com/phpstan/phpstan/discussions",
+                "issues": "https://github.com/phpstan/phpstan/issues",
+                "security": "https://github.com/phpstan/phpstan/security/policy",
+                "source": "https://github.com/phpstan/phpstan-src"
+            },
+            "funding": [
+                {
+                    "url": "https://github.com/ondrejmirtes",
+                    "type": "github"
+                },
+                {
+                    "url": "https://github.com/phpstan",
+                    "type": "github"
+                }
+            ],
+            "time": "2026-02-28T20:30:03+00:00"
+        },
         {
             "name": "phpunit/php-code-coverage",
             "version": "7.0.17",
@@ -4818,6 +4965,69 @@
             ],
             "time": "2024-11-10T20:33:58+00:00"
         },
+        {
+            "name": "szepeviktor/phpstan-wordpress",
+            "version": "v1.3.5",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/szepeviktor/phpstan-wordpress.git",
+                "reference": "7f8cfe992faa96b6a33bbd75c7bace98864161e7"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/szepeviktor/phpstan-wordpress/zipball/7f8cfe992faa96b6a33bbd75c7bace98864161e7",
+                "reference": "7f8cfe992faa96b6a33bbd75c7bace98864161e7",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^7.2 || ^8.0",
+                "php-stubs/wordpress-stubs": "^4.7 || ^5.0 || ^6.0",
+                "phpstan/phpstan": "^1.10.31",
+                "symfony/polyfill-php73": "^1.12.0"
+            },
+            "require-dev": {
+                "composer/composer": "^2.1.14",
+                "dealerdirect/phpcodesniffer-composer-installer": "^1.0",
+                "php-parallel-lint/php-parallel-lint": "^1.1",
+                "phpstan/phpstan-strict-rules": "^1.2",
+                "phpunit/phpunit": "^8.0 || ^9.0",
+                "szepeviktor/phpcs-psr-12-neutron-hybrid-ruleset": "^1.0",
+                "wp-coding-standards/wpcs": "3.1.0 as 2.3.0"
+            },
+            "suggest": {
+                "swissspidy/phpstan-no-private": "Detect usage of internal core functions, classes and methods"
+            },
+            "type": "phpstan-extension",
+            "extra": {
+                "phpstan": {
+                    "includes": [
+                        "extension.neon"
+                    ]
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "SzepeViktor\\PHPStan\\WordPress\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "description": "WordPress extensions for PHPStan",
+            "keywords": [
+                "PHPStan",
+                "code analyse",
+                "code analysis",
+                "static analysis",
+                "wordpress"
+            ],
+            "support": {
+                "issues": "https://github.com/szepeviktor/phpstan-wordpress/issues",
+                "source": "https://github.com/szepeviktor/phpstan-wordpress/tree/v1.3.5"
+            },
+            "time": "2024-06-28T22:27:19+00:00"
+        },
         {
             "name": "theseer/tokenizer",
             "version": "1.3.1",
diff --git a/inc/woocommerce.php b/inc/woocommerce.php
index 27fe5b025..e163e8665 100644
--- a/inc/woocommerce.php
+++ b/inc/woocommerce.php
@@ -30,11 +30,11 @@ function is_order_received_page()
 
 if (!function_exists('untrailingslashit')) {
     /**
-     * @since WooCommerce 2.2.0
-     * @param string $string
+     * @param string|null $string
      * @return string
+     * @since WooCommerce 2.2.0
      */
-    function untrailingslashit($string)
+    function untrailingslashit(?string $string): string
     {
         if ($string === null) {
             return '';
diff --git a/lib/payment-gateway/src/PaymentGateway.php b/lib/payment-gateway/src/PaymentGateway.php
index e1b07f77e..83ca66c76 100644
--- a/lib/payment-gateway/src/PaymentGateway.php
+++ b/lib/payment-gateway/src/PaymentGateway.php
@@ -67,6 +67,8 @@ public function __construct(
         unset($this->form_fields);
         unset($this->enabled);
 
+        // phpstan:ignore [wc-stub] process_admin_options is inherited from WC_Payment_Gateway but absent from stubs
+        // @phpstan-ignore-next-line
         add_action(
             'woocommerce_update_options_payment_gateways_' . $this->id,
             [$this, 'process_admin_options']
@@ -420,7 +422,7 @@ public function get_field_value($key, $field, $postData = [])
                 sprintf('Field "%1$s" is invalid: %2$s', $key, $exception->getMessage())
             );
 
-            return null;
+            return '';
         }
     }
 
diff --git a/lib/payment-gateway/src/PaymentGatewayModule.php b/lib/payment-gateway/src/PaymentGatewayModule.php
index 9d5de0fa0..1ecb7ebf6 100644
--- a/lib/payment-gateway/src/PaymentGatewayModule.php
+++ b/lib/payment-gateway/src/PaymentGatewayModule.php
@@ -48,7 +48,7 @@ public function services(): array
                  * prevent potential namespace conflicts when multiple plugins use this payment gateway library.
                  */
                 'payment_gateways.plugin_slug' => static function (ContainerInterface $container): string {
-                    /** @var PluginProperties $properties */
+                    /** @var PluginProperties $pluginProperties */
                     $pluginProperties = $container->get(Package::PROPERTIES);
 
                     return $pluginProperties->baseName();
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
new file mode 100644
index 000000000..b867be060
--- /dev/null
+++ b/phpstan.neon.dist
@@ -0,0 +1,29 @@
+parameters:
+  level: 5
+  dynamicConstantNames:
+    - M4W_PLUGIN_DIR
+    - M4W_FILE
+    - M4W_PLUGIN_URL
+  paths:
+    - mollie-payments-for-woocommerce.php
+    - lib/
+    - inc/
+    - src/
+  excludePaths:
+    - '*/node_modules/*'
+  bootstrapFiles:
+    - vendor/php-stubs/woocommerce-stubs/woocommerce-stubs.php
+    - vendor/php-stubs/woocommerce-stubs/woocommerce-packages-stubs.php
+    - vendor/php-stubs/woocommerce-subscriptions-stubs/woocommerce-subscriptions-stubs.php
+  ignoreErrors:
+    # apply_filters is variadic in WordPress but the stubs only declare 2 required params
+    - '#^Function apply_filters invoked with [0-9]+ parameters, [0-9]+ required\.$#'
+    # CustomOrdersTableController is an internal WooCommerce class not in stubs
+    - '#^(Class Automattic\\WooCommerce\\Internal\\DataStores\\Orders\\CustomOrdersTableController not found|Call to method custom_orders_table_usage_is_enabled\(\) on an unknown class)#'
+    # Vendored PSR container uses a namespaced path
+    - '#(unknown class|Call to method .+ on an unknown class|has unknown class) Mollie\\WooCommerce\\Vendor\\Psr\\Container\\ContainerInterface#'
+    # WC()->cart and WC()->customer are typed as non-nullable in stubs but can be null at runtime
+    - '#^(Property WooCommerce::\$cart \(WC_Cart\) in isset\(\) is not nullable|Left side of && is always true)\.$#'
+    # M4W_PLUGIN_DIR constant is defined at runtime in the main plugin file
+    - '#^Constant M4W_PLUGIN_DIR not found\.$#'
+
diff --git a/src/Assets/AssetsModule.php b/src/Assets/AssetsModule.php
index bbc575873..d5953b80b 100644
--- a/src/Assets/AssetsModule.php
+++ b/src/Assets/AssetsModule.php
@@ -518,7 +518,7 @@ function () use ($container, $pluginUrl, $pluginPath) {
         );
         add_action(
             'admin_init',
-            function () use ($container, $pluginVersion, $pluginUrl) {
+            function () use ($pluginVersion, $pluginUrl) {
                 if (is_admin()) {
                     global $current_section;
                     wp_register_script(
diff --git a/src/Buttons/AbstractExpressButton.php b/src/Buttons/AbstractExpressButton.php
index 83596238f..568f7a02d 100644
--- a/src/Buttons/AbstractExpressButton.php
+++ b/src/Buttons/AbstractExpressButton.php
@@ -18,6 +18,10 @@ public function bootstrap()
         $this->enqueueScripts();
     }
 
+    protected function enqueueScripts(): void
+    {
+    }
+
     protected function registerAjaxHandlers()
     {
         foreach ($this->getAjaxHandlers() as $action => $callback) {
diff --git a/src/Buttons/ApplePayButton/AppleAjaxRequests.php b/src/Buttons/ApplePayButton/AppleAjaxRequests.php
index 19fa8afd1..a50929eee 100644
--- a/src/Buttons/ApplePayButton/AppleAjaxRequests.php
+++ b/src/Buttons/ApplePayButton/AppleAjaxRequests.php
@@ -214,8 +214,8 @@ public function createWcOrder()
         $applePayRequestDataObject->orderData('productDetail');
 
         $cartItemKey = $cart->add_to_cart(
-            filter_input(INPUT_POST, 'productId'),
-            (bool) filter_input(INPUT_POST, 'productQuantity', FILTER_VALIDATE_INT)
+            (int)filter_input(INPUT_POST, 'productId', FILTER_SANITIZE_NUMBER_INT),
+            (int)filter_input(INPUT_POST, 'productQuantity', FILTER_VALIDATE_INT)
         );
         $this->addAddressesToOrder($applePayRequestDataObject);
 
@@ -300,7 +300,7 @@ protected function whichCalculateTotals(
      * @param      $productId
      * @param      $productQuantity
      * @param      $customerAddress
-     * @param null $shippingMethod
+     * @param mixed $shippingMethod
      */
     protected function calculateTotalsSingleProduct(
         $productId,
@@ -405,6 +405,8 @@ protected function cartShippingMethods(
     ): array {
 
         $shippingMethodsArray = [];
+        // phpstan:ignore [wc-stub] WC()->shipping is WC_Shipping|null at runtime; WooCommerce stubs declare it non-nullable
+        // @phpstan-ignore-next-line
         $shippingMethods = WC()->shipping->calculate_shipping(
             $this->getShippingPackages(
                 $customerAddress,
@@ -451,6 +453,8 @@ protected function getShippingPackages($customerAddress, $total)
         $packages = [];
         $packages[0]['contents'] = WC()->cart->cart_contents;
         $packages[0]['contents_cost'] = $total;
+        // phpstan:ignore [wc-stub] WC()->session exposes applied_coupon as a dynamic property; WC session stubs lack coverage
+        // @phpstan-ignore-next-line
         $packages[0]['applied_coupons'] = WC()->session->applied_coupon;
         $packages[0]['destination']['country'] = $customerAddress['country'];
         $packages[0]['destination']['state'] = '';
@@ -516,7 +520,7 @@ protected function cartCalculationResults(
      * method
      *
      * @param      $customerAddress
-     * @param null $shippingMethodId
+     * @param mixed $shippingMethodId
      */
     protected function calculateTotalsCartPage(
         $customerAddress = null,
@@ -689,7 +693,7 @@ function ($result, $order_id) {
                     wp_send_json_error(
                         $this->responseTemplates->authorizationResultResponse(
                             'STATUS_FAILURE',
-                            0,
+                            '0',
                             [['errorCode' => 'unknown']]
                         )
                     );
diff --git a/src/Buttons/ApplePayButton/ApplePayDataObjectHttp.php b/src/Buttons/ApplePayButton/ApplePayDataObjectHttp.php
index 8a5dcf667..a496e9036 100644
--- a/src/Buttons/ApplePayButton/ApplePayDataObjectHttp.php
+++ b/src/Buttons/ApplePayButton/ApplePayDataObjectHttp.php
@@ -6,6 +6,9 @@
 
 use Psr\Log\LoggerInterface as Logger;
 
+/**
+ * @phpcs:disable Inpsyde.CodeQuality.PropertyPerClassLimit.TooManyProperties
+ */
 class ApplePayDataObjectHttp
 {
     /**
@@ -77,6 +80,7 @@ public function hasErrors()
     {
         return !empty($this->errors);
     }
+
     /**
      * Returns errors
      * @return array
@@ -179,7 +183,7 @@ public function orderData($callerPage)
             !array_key_exists('emailAddress', $data[PropertiesDictionary::SHIPPING_CONTACT])
             || !$data[PropertiesDictionary::SHIPPING_CONTACT]['emailAddress']
         ) {
-            $this->errors[] =  [
+            $this->errors[] = [
                 'errorCode' => PropertiesDictionary::SHIPPING_CONTACT_INVALID,
                 'contactField' => 'emailAddress',
             ];
@@ -279,8 +283,8 @@ protected function simplifiedAddress($contactInfo)
      * are not empty.
      * If not it adds a contactField error to the object's error list
      *
-     * @param array  $post      The address to check
-     * @param array  $required  The required fields for the given address
+     * @param array $post The address to check
+     * @param array $required The required fields for the given address
      * @param string $errorCode Either shipping or billing kind
      *
      * @return bool
@@ -304,8 +308,7 @@ protected function addressHasRequiredFieldsValues(
                 $this->logger->debug(
                     sprintf('ApplePay Data Error: Missing value for %s', $requiredField)
                 );
-                $this->errors[]
-                    = [
+                $this->errors[] = [
                     'errorCode' => $errorCode,
                     'contactField' => $errorValue,
                 ];
@@ -318,7 +321,7 @@ protected function addressHasRequiredFieldsValues(
     /**
      * Returns the address details for after authorization steps
      *
-     * @param array  $data
+     * @param array $data
      *
      * @param string $errorCode differentiates between billing and shipping information
      *
diff --git a/src/Buttons/ApplePayButton/ApplePayDirectHandler.php b/src/Buttons/ApplePayButton/ApplePayDirectHandler.php
index 53bd3f2b8..7ff8a4485 100644
--- a/src/Buttons/ApplePayButton/ApplePayDirectHandler.php
+++ b/src/Buttons/ApplePayButton/ApplePayDirectHandler.php
@@ -11,6 +11,8 @@ class ApplePayDirectHandler
     /**
      * @var AdminNotice
      */
+    // phpstan:ignore [dead-code] injected via constructor but never read; kept in case future methods need admin notice access
+    // @phpstan-ignore-next-line
     private $adminNotice;
     /**
      * @var AppleAjaxRequests
diff --git a/src/Buttons/ApplePayButton/ApplePayExpressButton.php b/src/Buttons/ApplePayButton/ApplePayExpressButton.php
index a0f2297f0..582919429 100644
--- a/src/Buttons/ApplePayButton/ApplePayExpressButton.php
+++ b/src/Buttons/ApplePayButton/ApplePayExpressButton.php
@@ -31,6 +31,8 @@ public function getButtonComponent(): string
     public function canShow(): bool
     {
         return !empty($_SERVER['HTTPS']) &&
+            // phpstan:ignore [dead-code] isEnabledInSettings() is called but not declared in this class or its ancestors; likely missing trait or interface method
+            // @phpstan-ignore-next-line
             $this->isEnabledInSettings();
     }
 
@@ -42,6 +44,8 @@ public function getAjaxHandlers(): array
     public function getScriptData(): array
     {
         return [
+            // phpstan:ignore [dead-code] getCountryCode() is called but not declared in this class or its ancestors; likely missing trait or interface method
+            // @phpstan-ignore-next-line
             'shop' => ['countryCode' => $this->getCountryCode()],
             'ajaxUrl' => admin_url('admin-ajax.php'),
             'nonce' => wp_create_nonce('mollie_applepay'),
diff --git a/src/Buttons/ApplePayButton/ResponsesToApple.php b/src/Buttons/ApplePayButton/ResponsesToApple.php
index d09608e52..82c570d7f 100644
--- a/src/Buttons/ApplePayButton/ResponsesToApple.php
+++ b/src/Buttons/ApplePayButton/ResponsesToApple.php
@@ -14,7 +14,7 @@ class ResponsesToApple
      */
     protected $logger;
     /**
-     * @var
+     * @var mixed
      */
     protected $deprecatedAppleHelper;
 
diff --git a/src/Buttons/PayPalButton/PayPalAjaxRequests.php b/src/Buttons/PayPalButton/PayPalAjaxRequests.php
index 56829ac55..d634f8d5b 100644
--- a/src/Buttons/PayPalButton/PayPalAjaxRequests.php
+++ b/src/Buttons/PayPalButton/PayPalAjaxRequests.php
@@ -9,13 +9,12 @@
 use Mollie\WooCommerce\Notice\NoticeInterface;
 use Mollie\WooCommerce\Shared\GatewaySurchargeHandler;
 use Psr\Log\LoggerInterface as Logger;
-use Psr\Log\LogLevel;
 use WC_Data_Exception;
 
 class PayPalAjaxRequests
 {
     /**
-     * @var
+     * @var mixed
      */
     protected $gateway;
     /**
@@ -135,7 +134,6 @@ public function createWcOrderFromCart()
         $lockKey = 'mollie_paypal_cart_order_lock';
         if (WC()->session->get($lockKey)) {
             wp_send_json_error('Duplicate request');
-            return;
         }
         WC()->session->set($lockKey, true);
 
@@ -243,7 +241,7 @@ protected function processOrderPayment($orderId)
      * Handles the order creation in cart page
      *
      * @return array
-     * @throws Exception
+     * @throws \Exception
      */
     protected function createOrderFromCart()
     {
@@ -257,7 +255,6 @@ protected function createOrderFromCart()
     /**
      * Checks if the nonce in the data object is valid
      *
-     * @param PayPalDataObjectHttp $PayPalRequestDataObject
      */
     protected function isNonceValid(): bool
     {
diff --git a/src/Buttons/PayPalButton/PayPalDataObjectHttp.php b/src/Buttons/PayPalButton/PayPalDataObjectHttp.php
index 66784ee3a..9c23cdc29 100644
--- a/src/Buttons/PayPalButton/PayPalDataObjectHttp.php
+++ b/src/Buttons/PayPalButton/PayPalDataObjectHttp.php
@@ -5,7 +5,6 @@
 namespace Mollie\WooCommerce\Buttons\PayPalButton;
 
 use Psr\Log\LoggerInterface as Logger;
-use Psr\Log\LogLevel;
 
 class PayPalDataObjectHttp
 {
@@ -138,7 +137,7 @@ protected function assignDataObjectValues(array $data)
      * Selector for the different filters to apply to each field
      * @param $value
      *
-     * @return int
+     * @return int|false
      */
     protected function filterType($value)
     {
diff --git a/src/Buttons/PayPalButton/PayPalExpressButton.php b/src/Buttons/PayPalButton/PayPalExpressButton.php
index 52eab99e9..801a247fa 100644
--- a/src/Buttons/PayPalButton/PayPalExpressButton.php
+++ b/src/Buttons/PayPalButton/PayPalExpressButton.php
@@ -167,6 +167,7 @@ private function registerCartPageHook(): void
     private function isVirtualProduct(\WC_Product $product): bool
     {
         if ($product->is_type('variable')) {
+            assert($product instanceof \WC_Product_Variable);
             foreach ($product->get_available_variations() as $variation) {
                 if ($variation['is_virtual']) {
                     return true;
diff --git a/src/Buttons/PayPalButton/WCOrderCalculator.php b/src/Buttons/PayPalButton/WCOrderCalculator.php
index 259eb1ad6..2e717d050 100644
--- a/src/Buttons/PayPalButton/WCOrderCalculator.php
+++ b/src/Buttons/PayPalButton/WCOrderCalculator.php
@@ -5,7 +5,6 @@
 namespace Mollie\WooCommerce\Buttons\PayPalButton;
 
 use WC_Order;
-use WC_Order_Item_Product;
 
 class WCOrderCalculator extends WC_Order
 {
@@ -30,23 +29,23 @@ public function calculate_totals($and_taxes = true)
 
         // Sum shipping costs.
         foreach ($this->get_shipping_methods() as $shipping) {
-            $shipping_total += $this->round($shipping->get_total(), wc_get_price_decimals());
+            $shipping_total += $this->round((float)$shipping->get_total(), wc_get_price_decimals());
         }
 
-        $this->set_shipping_total($shipping_total);
+        $this->set_shipping_total((string)$shipping_total);
 
         // Sum fee costs.
         foreach ($this->get_fees() as $item) {
-            $fee_total = $item->get_total();
+            $fee_total = (float)$item->get_total();
 
             if (0 > $fee_total) {
                 $max_discount = $this->round($cart_total + $fees_total + $shipping_total, wc_get_price_decimals()) * -1;
 
                 if ($fee_total < $max_discount && 0 > $max_discount) {
-                    $item->set_total($max_discount);
+                    $item->set_total((string)$max_discount);
                 }
             }
-            $fees_total += $item->get_total();
+            $fees_total += (float)$item->get_total();
         }
 
         // Calculate taxes for items, shipping, discounts. Note; this also triggers save().
@@ -56,6 +55,8 @@ public function calculate_totals($and_taxes = true)
 
          // Sum taxes again so we can work out how much tax was discounted. This uses original values, not those possibly rounded to 2dp.
         foreach ($this->get_items() as $item) {
+            // phpstan:ignore [wc-stub] get_items() returns WC_Order_Item[] but get_taxes() is only typed on product/shipping subtypes
+            // @phpstan-ignore-next-line
             $taxes = $item->get_taxes();
 
             foreach ($taxes['total'] as $tax_rate_id => $tax) {
@@ -67,9 +68,15 @@ public function calculate_totals($and_taxes = true)
             }
         }
 
-          $this->set_discount_total($this->round($cart_subtotal - $cart_total, wc_get_price_decimals()));
-          $this->set_discount_tax(wc_round_tax_total($cart_subtotal_tax - $cart_total_tax));
-          $this->set_total($this->round($cart_total + $fees_total + $this->get_shipping_total() + $this->get_cart_tax() + $this->get_shipping_tax(), wc_get_price_decimals()));
+        $this->set_discount_total((string)$this->round($cart_subtotal - $cart_total, wc_get_price_decimals()));
+        $this->set_discount_tax((string)wc_round_tax_total($cart_subtotal_tax - $cart_total_tax));
+        $this->set_total(
+            (string)$this->round(
+                $cart_total + $fees_total + (float)$this->get_shipping_total() + (float)$this->get_cart_tax(
+                ) + (float)$this->get_shipping_tax(),
+                wc_get_price_decimals()
+            )
+        );
 
           do_action('woocommerce_order_after_calculate_totals', $and_taxes, $this);
 
@@ -86,6 +93,8 @@ public function update_taxes()
         $saved_rate_ids = [];
 
         foreach ($this->get_items([ 'line_item', 'fee' ]) as $item_id => $item) {
+            // phpstan:ignore [wc-stub] get_items() returns WC_Order_Item[] but get_taxes() is only typed on product/shipping subtypes
+            // @phpstan-ignore-next-line
             $taxes = $item->get_taxes();
             foreach ($taxes['total'] as $tax_rate_id => $tax) {
                 $tax_amount = $this->round_line_tax($tax, false);
@@ -114,8 +123,12 @@ public function update_taxes()
                 continue;
             }
             $saved_rate_ids[] = $tax->get_rate_id();
-            $tax->set_tax_total(isset($cart_taxes[ $tax->get_rate_id() ]) ? $cart_taxes[ $tax->get_rate_id() ] : 0);
-            $tax->set_shipping_tax_total(! empty($shipping_taxes[ $tax->get_rate_id() ]) ? $shipping_taxes[ $tax->get_rate_id() ] : 0);
+            $tax->set_tax_total(
+                (string)(isset($cart_taxes[$tax->get_rate_id()]) ? $cart_taxes[$tax->get_rate_id()] : 0)
+            );
+            $tax->set_shipping_tax_total(
+                (string)(!empty($shipping_taxes[$tax->get_rate_id()]) ? $shipping_taxes[$tax->get_rate_id()] : 0)
+            );
             $tax->save();
         }
 
@@ -125,17 +138,21 @@ public function update_taxes()
         foreach ($new_rate_ids as $tax_rate_id) {
             $item = new \WC_Order_Item_Tax();
             $item->set_rate($tax_rate_id);
-            $item->set_tax_total(isset($cart_taxes[ $tax_rate_id ]) ? $cart_taxes[ $tax_rate_id ] : 0);
-            $item->set_shipping_tax_total(! empty($shipping_taxes[ $tax_rate_id ]) ? $shipping_taxes[ $tax_rate_id ] : 0);
+            $item->set_tax_total((string)(isset($cart_taxes[$tax_rate_id]) ? $cart_taxes[$tax_rate_id] : 0));
+            $item->set_shipping_tax_total(
+                (string)(!empty($shipping_taxes[$tax_rate_id]) ? $shipping_taxes[$tax_rate_id] : 0)
+            );
             $this->add_item($item);
         }
 
-        $this->set_shipping_tax(array_sum($shipping_taxes));
-        $this->set_cart_tax(array_sum($cart_taxes));
+        $this->set_shipping_tax((string)array_sum($shipping_taxes));
+        $this->set_cart_tax((string)array_sum($cart_taxes));
     }
 
     public function add_product($product, $qty = 1, $args = [])
     {
+        // phpstan:ignore [wc-stub] parent WC_Order::add_product() declares $product as WC_Product; override loosens the type to allow null/false
+        // @phpstan-ignore-next-line
         if ($product) {
             $default_args = [
                 'name' => $product->get_name(),
diff --git a/src/Gateway/GatewayModule.php b/src/Gateway/GatewayModule.php
index a6e8e0d12..61643aa1c 100644
--- a/src/Gateway/GatewayModule.php
+++ b/src/Gateway/GatewayModule.php
@@ -20,9 +20,7 @@
 use Mollie\WooCommerce\Gateway\Voucher\MaybeDisableGateway;
 use Mollie\WooCommerce\Payment\MollieOrderService;
 use Mollie\WooCommerce\PaymentMethods\Constants;
-use Mollie\WooCommerce\PaymentMethods\IconFactory;
 use Mollie\WooCommerce\PaymentMethods\PaymentMethodI;
-use Mollie\WooCommerce\Settings\Settings;
 use Mollie\WooCommerce\Shared\Data;
 use Mollie\WooCommerce\Shared\GatewaySurchargeHandler;
 use Mollie\WooCommerce\Shared\SharedDataDictionary;
@@ -173,20 +171,22 @@ static function ($paymentContext) {
                 if (!$title) {
                     return;
                 }
+                // phpstan:ignore [wc-stub] $paymentContext is passed via WC REST action with no declared type; ->order is a WC_Order
+                // @phpstan-ignore-next-line
                 $order = $paymentContext->order;
                 $order->set_payment_method_title($title);
                 $order->save();
             }
         );
         add_action('add_meta_boxes_woocommerce_page_wc-orders', [$this, 'addShopOrderMetabox'], 10);
-        add_filter('woocommerce_checkout_fields', static function ($fields) use ($container) {
+        add_filter('woocommerce_checkout_fields', static function ($fields) {
             if (!isset($fields['billing']['billing_phone']) || !$fields['billing']['billing_phone']['required']) {
                 update_option('mollie_wc_is_phone_required_flag', false);
             } else {
                 update_option('mollie_wc_is_phone_required_flag', true);
             }
             return $fields;
-        }, 10, 3);
+        }, 10, 1);
 
         add_action('init', static function () use ($container) {
             $paymentMethods = $container->get('gateway.paymentMethods');
@@ -523,7 +523,7 @@ public function paymentButtonsBootstrap(ContainerInterface $container): void
      *
      * @return array
      */
-    protected function instantiatePaymentMethods(): array
+    public function instantiatePaymentMethods(): array
     {
         $paymentMethods = [];
         $allGatewayClassNames = SharedDataDictionary::GATEWAY_CLASSNAMES;
@@ -547,10 +547,6 @@ protected function instantiatePaymentMethods(): array
 
     /**
      * @param string $id
-     * @param IconFactory $iconFactory
-     * @param Settings $settingsHelper
-     * @param Surcharge $surchargeService
-     * @param array $paymentMethods
      * @return PaymentMethodI | array
      */
     public function buildPaymentMethod(
diff --git a/src/Gateway/MolliePaymentGatewayHandler.php b/src/Gateway/MolliePaymentGatewayHandler.php
index e8fcb488a..1ae392a0d 100644
--- a/src/Gateway/MolliePaymentGatewayHandler.php
+++ b/src/Gateway/MolliePaymentGatewayHandler.php
@@ -10,7 +10,6 @@
 use Mollie\WooCommerce\Payment\MollieObject;
 use Mollie\WooCommerce\Payment\MollieOrderService;
 use Mollie\WooCommerce\Payment\PaymentFactory;
-use Mollie\WooCommerce\Payment\PaymentProcessor;
 use Mollie\WooCommerce\PaymentMethods\InstructionStrategies\OrderInstructionsManager;
 use Mollie\WooCommerce\PaymentMethods\PaymentMethodI;
 use Mollie\WooCommerce\SDK\HttpResponse;
@@ -190,6 +189,8 @@ public function is_available($gateway): bool
             return true;
         }
 
+        // phpstan:ignore [wc-stub] WC()->cart is WC_Cart|null at runtime; WooCommerce stubs declare it non-nullable
+        // @phpstan-ignore-next-line
         $order_total = WC()->cart ? WC()->cart->get_total('edit') : 0;
         $currency = $this->getCurrencyFromOrder();
         $billingCountry = $this->getBillingCountry();
@@ -422,10 +423,12 @@ public function activePaymentObject($orderId, $useCache): Payment
      * @param      $title
      * @param null $id
      *
-     * @return string|void
+     * @return string
      */
     public function onOrderReceivedTitle($title, $id = null)
     {
+        // phpstan:ignore [wc-stub] get_the_ID() returns int|false; comparison with nullable $id triggers a false-positive
+        // @phpstan-ignore-next-line
         if (is_order_received_page() && get_the_ID() === $id) {
             $order = false;
             $orderReceived = get_query_var('order-received');
@@ -526,9 +529,9 @@ public function onOrderReceivedTitle($title, $id = null)
 
     /**
      * @param          $text
-     * @param WC_Order| null $order
+     * @param WC_Order|null $order
      *
-     * @return string|void
+     * @return string
      */
     public function onOrderReceivedText($text, $order)
     {
@@ -583,6 +586,8 @@ public function getCurrencyFromOrder()
      */
     public function getBillingCountry()
     {
+        // phpstan:ignore [wc-stub] WC()->customer is WC_Customer|null at runtime; WooCommerce stubs declare it non-nullable
+        // @phpstan-ignore-next-line
         $customerExistsAndHasCountry = WC()->customer && !empty(WC()->customer->get_billing_country());
         $fallbackToShopCountry = wc_get_base_location()['country'];
         $billingCountry = $customerExistsAndHasCountry ? WC()->customer->get_billing_country() : $fallbackToShopCountry;
@@ -642,6 +647,8 @@ protected function checkEnabledNorDirectDebit($gateway): bool
      */
     protected function cartAmountAvailable()
     {
+        // phpstan:ignore [wc-stub] WC()->cart is WC_Cart|null at runtime; WooCommerce stubs declare it non-nullable
+        // @phpstan-ignore-next-line
         return WC()->cart && WC()->cart->get_total('edit') > 0;
     }
 
diff --git a/src/Gateway/Refund/RefundLineItemsBuilder.php b/src/Gateway/Refund/RefundLineItemsBuilder.php
index 21908786a..df79294dd 100644
--- a/src/Gateway/Refund/RefundLineItemsBuilder.php
+++ b/src/Gateway/Refund/RefundLineItemsBuilder.php
@@ -106,10 +106,9 @@ private function buildLineItem(
     ) {
 
         $toRefundItemQuantity = abs((int) $toRefundItem->get_quantity());
-        $toRefundItemAmount = number_format(
-            abs($toRefundItem->get_total() + $toRefundItem->get_total_tax()),
-            2
-        );
+        // @phpstan-ignore-next-line
+        $toRefundItemTotal = (float)$toRefundItem->get_total() + (float)$toRefundItem->get_total_tax();
+        $toRefundItemAmount = number_format(abs($toRefundItemTotal), 2);
         $toRefundRemoteItemPrice = property_exists($toRefundRemoteItem->unitPrice, 'value') && $toRefundRemoteItem->unitPrice->value !== null
             ? $toRefundRemoteItem->unitPrice->value
             : 0;
diff --git a/src/Gateway/Surcharge.php b/src/Gateway/Surcharge.php
index 61b5c2c00..9417b299f 100644
--- a/src/Gateway/Surcharge.php
+++ b/src/Gateway/Surcharge.php
@@ -288,8 +288,6 @@ protected function name_fixed_fee_percentage($paymentMethod)
         if (
             !$paymentMethod->getProperty(self::FIXED_FEE)
             || !$paymentMethod->getProperty(self::PERCENTAGE)
-            || $paymentMethod->getProperty(self::FIXED_FEE) === ''
-            || $paymentMethod->getProperty(self::PERCENTAGE) === ''
             || $paymentMethod->getProperty(self::PERCENTAGE) <= 0
             || $paymentMethod->getProperty(self::FIXED_FEE) <= 0
         ) {
diff --git a/src/Gateway/Voucher/MaybeDisableGateway.php b/src/Gateway/Voucher/MaybeDisableGateway.php
index 845d0f505..c896a870f 100644
--- a/src/Gateway/Voucher/MaybeDisableGateway.php
+++ b/src/Gateway/Voucher/MaybeDisableGateway.php
@@ -4,9 +4,6 @@
 
 namespace Mollie\WooCommerce\Gateway\Voucher;
 
-use Inpsyde\PaymentGateway\PaymentGateway;
-use Mollie\WooCommerce\Gateway\MolliePaymentGatewayHandler;
-use Mollie\WooCommerce\Payment\PaymentProcessor;
 use Mollie\WooCommerce\PaymentMethods\Voucher;
 
 class MaybeDisableGateway
@@ -45,6 +42,8 @@ public function haveCartProductsCategories(): bool
         }
 
         $cart = WC()->cart;
+        // phpstan:ignore [wc-stub] WC()->cart is WC_Cart|null at runtime; WooCommerce stubs declare it non-nullable
+        // @phpstan-ignore-next-line
         if (!$cart) {
             return false;
         }
diff --git a/src/Gateway/inc/services.php b/src/Gateway/inc/services.php
index 6c21a431e..64b3f7f70 100644
--- a/src/Gateway/inc/services.php
+++ b/src/Gateway/inc/services.php
@@ -12,19 +12,20 @@
 use Mollie\WooCommerce\Buttons\PayPalButton\PayPalButtonHandler;
 use Mollie\WooCommerce\Buttons\PayPalButton\PayPalExpressButton;
 use Mollie\WooCommerce\Gateway\DeprecatedGatewayBuilder;
+use Mollie\WooCommerce\Gateway\GatewayModule;
 use Mollie\WooCommerce\Gateway\Refund\OrderItemsRefunder;
 use Mollie\WooCommerce\Gateway\Refund\RefundLineItemsBuilder;
 use Mollie\WooCommerce\Gateway\Refund\RefundProcessor;
 use Mollie\WooCommerce\Gateway\Surcharge;
 use Mollie\WooCommerce\Notice\AdminNotice;
 use Mollie\WooCommerce\Payment\MollieOrderService;
-use Mollie\WooCommerce\Payment\Webhooks\WebhookHandler;
-use Mollie\WooCommerce\PaymentMethods\InstructionStrategies\OrderInstructionsManager;
 use Mollie\WooCommerce\Payment\PaymentCheckoutRedirectService;
 use Mollie\WooCommerce\Payment\PaymentFactory;
 use Mollie\WooCommerce\Payment\PaymentProcessor;
+use Mollie\WooCommerce\Payment\Webhooks\WebhookHandler;
 use Mollie\WooCommerce\PaymentMethods\Constants;
 use Mollie\WooCommerce\PaymentMethods\IconFactory;
+use Mollie\WooCommerce\PaymentMethods\InstructionStrategies\OrderInstructionsManager;
 use Mollie\WooCommerce\PaymentMethods\PaymentMethodI;
 use Mollie\WooCommerce\SDK\Api;
 use Mollie\WooCommerce\SDK\HttpResponse;
@@ -45,7 +46,7 @@
         },
         'gateway.paymentMethods' => static function (ContainerInterface $container): array {
             $onlyAvailableMethods = $container->get('gateway.getPaymentMethodsAfterFeatureFlag');
-            $allPaymentMethods = (new self())->instantiatePaymentMethods();
+            $allPaymentMethods = (new GatewayModule())->instantiatePaymentMethods();
             //we want only the methods after the feature flags
             return array_filter($allPaymentMethods, static function ($method, $key) use ($onlyAvailableMethods) {
                 return array_key_exists($key, $onlyAvailableMethods);
@@ -305,6 +306,8 @@ static function ($order_id) use ($instructionsManager, $paymentGateway, $depreca
                         }
 
                         // Empty cart
+                        // phpstan:ignore [wc-stub] WC()->cart is WC_Cart|null at runtime; WooCommerce stubs declare it non-nullable
+                        // @phpstan-ignore-next-line
                         if (WC()->cart) {
                             WC()->cart->empty_cart();
                         }
@@ -393,6 +396,9 @@ static function ($filteredOption) {
 
     ];
 
-    $paymentMethods = (new self())->instantiatePaymentMethods();
-    return array_merge($services, (new self())->providePaymentMethodServices(...array_values($paymentMethods)));
+    $paymentMethods = (new GatewayModule())->instantiatePaymentMethods();
+    return array_merge(
+        $services,
+        (new GatewayModule())->providePaymentMethodServices(...array_values($paymentMethods))
+    );
 };
diff --git a/src/Log/WcPsrLoggerAdapter.php b/src/Log/WcPsrLoggerAdapter.php
index 52c8f68ce..f8d233167 100644
--- a/src/Log/WcPsrLoggerAdapter.php
+++ b/src/Log/WcPsrLoggerAdapter.php
@@ -91,9 +91,7 @@ public function log($level, $message, array $context = [])
         }
         $context['source'] = $this->loggerSource;
 
-        $interpolatedMessage = is_string($message)
-            ? $this->interpolate($message, $this->getReplacements($context))
-            : $message;
+        $interpolatedMessage = $this->interpolate((string)$message, $this->getReplacements($context));
 
         $this->wcLogger->log($level, $interpolatedMessage, $context);
     }
diff --git a/src/MerchantCapture/Capture/Type/ManualCapture.php b/src/MerchantCapture/Capture/Type/ManualCapture.php
index 59243b275..ba18961c0 100644
--- a/src/MerchantCapture/Capture/Type/ManualCapture.php
+++ b/src/MerchantCapture/Capture/Type/ManualCapture.php
@@ -5,7 +5,6 @@
 namespace Mollie\WooCommerce\MerchantCapture\Capture\Type;
 
 use Mollie\WooCommerce\MerchantCapture\Capture\Action\CapturePayment;
-use Mollie\WooCommerce\Payment\MollieOrderService;
 use Psr\Container\ContainerInterface;
 
 class ManualCapture
@@ -65,9 +64,8 @@ public function sendManualCaptureMode(array $paymentData): array
         return $paymentData;
     }
 
-    public function manualCapture(\WC_Order $order)
+    public function manualCapture(\WC_Order $order): void
     {
-
         ($this->container->get(CapturePayment::class))($order->get_id());
         //give paid webhook time to arrive so that updated correctly bevor showing the order in the backend
         sleep(3);
diff --git a/src/Payment/LineItems/OrderLines.php b/src/Payment/LineItems/OrderLines.php
index a436e76fc..ed8f78a10 100644
--- a/src/Payment/LineItems/OrderLines.php
+++ b/src/Payment/LineItems/OrderLines.php
@@ -16,7 +16,7 @@ class OrderLines implements LineItemProvider
     /**
      * Formatted order lines.
      *
-     * @var $order_lines
+     * @var array
      */
     private $order_lines =  [];
 
@@ -182,7 +182,7 @@ private function process_items()
                 }
 
                 if ($product instanceof \WC_Product && $product->get_image_id()) {
-                    $productImage = wp_get_attachment_image_src($product->get_image_id(), 'full');
+                    $productImage = wp_get_attachment_image_src((int)$product->get_image_id(), 'full');
                     if (isset($productImage[0]) && wc_is_valid_url($productImage[0])) {
                         $mollie_order_item['imageUrl'] = $productImage[0];
                     }
@@ -214,7 +214,10 @@ private function process_shipping()
             foreach ($shipping_methods as $shipping_method) {
                 $vatRate = 0;
                 if ($shipping_method->get_total_tax() > 0 && $shipping_method->get_total() > 0) {
-                    $vatRate = round($shipping_method->get_total_tax() / $shipping_method->get_total(), 4) * 100;
+                    $vatRate = round(
+                        (float)$shipping_method->get_total_tax() / (float)$shipping_method->get_total(),
+                        4
+                    ) * 100;
                 }
                 $shipping = [
                     'type' => 'shipping_fee',
@@ -223,15 +226,24 @@ private function process_shipping()
                     'vatRate' => $vatRate,
                     'unitPrice' =>  [
                         'currency' => $this->currency,
-                        'value' => $this->dataHelper->formatCurrencyValue($shipping_method->get_total() + $shipping_method->get_total_tax(), $this->currency),
+                        'value' => $this->dataHelper->formatCurrencyValue(
+                            (float)$shipping_method->get_total() + (float)$shipping_method->get_total_tax(),
+                            $this->currency
+                        ),
                     ],
                     'totalAmount' =>  [
                         'currency' => $this->currency,
-                        'value' => $this->dataHelper->formatCurrencyValue($shipping_method->get_total() + $shipping_method->get_total_tax(), $this->currency),
+                        'value' => $this->dataHelper->formatCurrencyValue(
+                            (float)$shipping_method->get_total() + (float)$shipping_method->get_total_tax(),
+                            $this->currency
+                        ),
                     ],
                     'vatAmount' =>  [
                         'currency' => $this->currency,
-                        'value' => $this->dataHelper->formatCurrencyValue($shipping_method->get_total_tax(), $this->currency),
+                        'value' => $this->dataHelper->formatCurrencyValue(
+                            (float)$shipping_method->get_total_tax(),
+                            $this->currency
+                        ),
                     ],
                     'metadata' => [
                         'order_item_id' => $shipping_method->get_id(),
@@ -314,18 +326,27 @@ private function process_gift_cards()
     {
         if (!empty($this->order->get_items('gift_card'))) {
             foreach ($this->order->get_items('gift_card') as $cart_gift_card) {
+                // phpstan:ignore [wc-stub] WC gift card item's get_amount() is not declared in stubs
+                // @phpstan-ignore-next-line
+                $giftCardAmount = $cart_gift_card->get_amount();
                 $gift_card = [
                     'type' => 'gift_card',
                     'name' => $cart_gift_card->get_name(),
                     'unitPrice' => [
                         'currency' => $this->currency,
-                        'value' =>  $this->dataHelper->formatCurrencyValue(-$cart_gift_card->get_amount(), $this->currency),
+                        'value' => $this->dataHelper->formatCurrencyValue(
+                            -$giftCardAmount,
+                            $this->currency
+                        ),
                     ],
                     'vatRate' => 0,
                     'quantity' => 1,
                     'totalAmount' => [
                         'currency' => $this->currency,
-                        'value' =>  $this->dataHelper->formatCurrencyValue(-$cart_gift_card->get_amount(), $this->currency),
+                        'value' => $this->dataHelper->formatCurrencyValue(
+                            -$giftCardAmount,
+                            $this->currency
+                        ),
                     ],
                     'vatAmount' => [
                         'currency' => $this->currency,
@@ -366,6 +387,8 @@ private function get_item_name($cart_item)
      *
      * @return integer $item_tax_amount Item tax amount.
      */
+    // phpstan:ignore [dead-code] private method appears unused; kept for potential future use
+    // @phpstan-ignore-next-line
     private function get_item_tax_amount($cart_item)
     {
         return $cart_item['line_tax'];
diff --git a/src/Payment/LineItems/PaymentLines.php b/src/Payment/LineItems/PaymentLines.php
index aaecb5cf1..a5ab75ec6 100644
--- a/src/Payment/LineItems/PaymentLines.php
+++ b/src/Payment/LineItems/PaymentLines.php
@@ -17,7 +17,7 @@ class PaymentLines implements LineItemProvider
     /**
      * Formatted order lines.
      *
-     * @var $order_lines
+     * @var array
      */
     private $order_lines =  [];
 
@@ -173,7 +173,7 @@ private function process_items()
                 }
 
                 if ($product instanceof \WC_Product && $product->get_image_id()) {
-                    $productImage = wp_get_attachment_image_src($product->get_image_id(), 'full');
+                    $productImage = wp_get_attachment_image_src((int)$product->get_image_id(), 'full');
                     if (isset($productImage[0]) && wc_is_valid_url($productImage[0])) {
                         $mollie_order_item['imageUrl'] = $productImage[0];
                     }
@@ -205,7 +205,10 @@ private function process_shipping()
             foreach ($shipping_methods as $shipping_method) {
                 $vatRate = 0;
                 if ($shipping_method->get_total_tax() > 0 && $shipping_method->get_total() > 0) {
-                    $vatRate = round($shipping_method->get_total_tax() / $shipping_method->get_total(), 4) * 100;
+                    $vatRate = round(
+                        (float)$shipping_method->get_total_tax() / (float)$shipping_method->get_total(),
+                        4
+                    ) * 100;
                 }
                 $shipping = [
                     'type' => 'shipping_fee',
@@ -214,15 +217,24 @@ private function process_shipping()
                     'vatRate' => $vatRate,
                     'unitPrice' =>  [
                         'currency' => $this->currency,
-                        'value' => $this->dataHelper->formatCurrencyValue($shipping_method->get_total() + $shipping_method->get_total_tax(), $this->currency),
+                        'value' => $this->dataHelper->formatCurrencyValue(
+                            (float)$shipping_method->get_total() + (float)$shipping_method->get_total_tax(),
+                            $this->currency
+                        ),
                     ],
                     'totalAmount' =>  [
                         'currency' => $this->currency,
-                        'value' => $this->dataHelper->formatCurrencyValue($shipping_method->get_total() + $shipping_method->get_total_tax(), $this->currency),
+                        'value' => $this->dataHelper->formatCurrencyValue(
+                            (float)$shipping_method->get_total() + (float)$shipping_method->get_total_tax(),
+                            $this->currency
+                        ),
                     ],
                     'vatAmount' =>  [
                         'currency' => $this->currency,
-                        'value' => $this->dataHelper->formatCurrencyValue($shipping_method->get_total_tax(), $this->currency),
+                        'value' => $this->dataHelper->formatCurrencyValue(
+                            (float)$shipping_method->get_total_tax(),
+                            $this->currency
+                        ),
                     ],
                 ];
 
@@ -300,18 +312,27 @@ private function process_gift_cards()
     {
         if (!empty($this->order->get_items('gift_card'))) {
             foreach ($this->order->get_items('gift_card') as $cart_gift_card) {
+                // phpstan:ignore [wc-stub] WC gift card item's get_amount() is not declared in stubs
+                // @phpstan-ignore-next-line
+                $giftCardAmount = $cart_gift_card->get_amount();
                 $gift_card = [
                     'type' => 'gift_card',
                     'description' => $cart_gift_card->get_name(),
                     'unitPrice' => [
                         'currency' => $this->currency,
-                        'value' =>  $this->dataHelper->formatCurrencyValue(-$cart_gift_card->get_amount(), $this->currency),
+                        'value' => $this->dataHelper->formatCurrencyValue(
+                            -$giftCardAmount,
+                            $this->currency
+                        ),
                     ],
                     'vatRate' => 0,
                     'quantity' => 1,
                     'totalAmount' => [
                         'currency' => $this->currency,
-                        'value' =>  $this->dataHelper->formatCurrencyValue(-$cart_gift_card->get_amount(), $this->currency),
+                        'value' => $this->dataHelper->formatCurrencyValue(
+                            -$giftCardAmount,
+                            $this->currency
+                        ),
                     ],
                     'vatAmount' => [
                         'currency' => $this->currency,
diff --git a/src/Payment/MollieObject.php b/src/Payment/MollieObject.php
index dda1bb111..f2e6a7ad9 100644
--- a/src/Payment/MollieObject.php
+++ b/src/Payment/MollieObject.php
@@ -11,9 +11,9 @@
 use Mollie\WooCommerce\SDK\Api;
 use Mollie\WooCommerce\Settings\Settings;
 use Mollie\WooCommerce\Shared\SharedDataDictionary;
+use Psr\Log\LoggerInterface as Logger;
 use WC_Order;
 use WC_Payment_Gateway;
-use Psr\Log\LoggerInterface as Logger;
 
 class MollieObject
 {
@@ -47,6 +47,8 @@ class MollieObject
     /**
      * @var null
      */
+    // phpstan:ignore [dead-code] typed @var null; kept as a placeholder — subclasses shadow this with properly typed versions
+    // @phpstan-ignore-next-line
     private $paymentMethod;
     protected RequestFactory $requestFactory;
 
@@ -415,7 +417,7 @@ public function getActiveMolliePayment($order_id, $use_cache = true)
                 );
             } catch (ApiException $exception) {
                 $this->logger->debug($exception->getMessage());
-                return;
+                return null;
             }
 
             return $this->getPaymentObjectPayment(
@@ -591,8 +593,12 @@ public function addMandateIdMetaToFirstPaymentSubscriptionOrder(
                     $subscriptions = wcs_get_subscriptions_for_renewal_order($order);
                 }
                 foreach ($subscriptions as $subscription) {
+                    // phpstan:ignore [mollie-stub] Mollie Payment object exposes id and mandateId as dynamic stdClass properties not covered by type definitions
+                    // @phpstan-ignore-next-line
                     $subscription->update_meta_data('_mollie_payment_id', $payment->id);
                     $subscription->update_meta_data('_mollie_mandate_id', $payment->mandateId);
+                    // phpstan:ignore [mollie-stub] Mollie Payment object exposes method as a dynamic property; also set_payment_method() may not be typed on WC_Subscription stubs
+                    // @phpstan-ignore-next-line
                     $subscription->set_payment_method('mollie_wc_gateway_' . $payment->method);
                     $subscription->save();
                     $subscriptionParentOrder = $subscription->get_parent();
@@ -722,6 +728,8 @@ function_exists('wcs_order_contains_renewal')
                 !empty($emails) && !empty($orderId)
                 && !empty($emails['WC_Email_Failed_Order'])
             ) {
+                // phpstan:ignore [wc-stub] WC_Email subclass accessed via mailer array; trigger() not typed on WC_Email base class in stubs
+                // @phpstan-ignore-next-line
                 $emails['WC_Email_Failed_Order']->trigger($orderId);
             }
         } elseif (mollieWooCommerceIsMollieGateway($gateway->id)) {
diff --git a/src/Payment/MollieOrder.php b/src/Payment/MollieOrder.php
index ba955b142..b107e399f 100644
--- a/src/Payment/MollieOrder.php
+++ b/src/Payment/MollieOrder.php
@@ -5,21 +5,17 @@
 namespace Mollie\WooCommerce\Payment;
 
 use Exception;
-use Inpsyde\PaymentGateway\PaymentGateway;
 use Mollie\Api\Exceptions\ApiException;
-use Mollie\Api\Resources\Payment;
 use Mollie\Api\Resources\Order;
+use Mollie\Api\Resources\Payment;
 use Mollie\Api\Resources\Refund;
 use Mollie\WooCommerce\Gateway\Refund\OrderItemsRefunder;
 use Mollie\WooCommerce\Gateway\Refund\PartialRefundException;
 use Mollie\WooCommerce\Payment\Request\RequestFactory;
-use Mollie\WooCommerce\PaymentMethods\Voucher;
 use Mollie\WooCommerce\SDK\Api;
 use Mollie\WooCommerce\Settings\Settings;
 use Mollie\WooCommerce\Shared\Data;
-use Mollie\WooCommerce\Shared\SharedDataDictionary;
 use Psr\Log\LoggerInterface as Logger;
-use Psr\Log\LogLevel;
 use UnexpectedValueException;
 use WC_Order;
 use WP_Error;
@@ -226,11 +222,14 @@ public function refund(WC_Order $order, $orderId, $paymentObject, $amount = null
             $totals = 0;
 
             foreach ($items as $itemId => $itemData) {
-                $totals += $itemData->get_total() + $itemData->get_total_tax();
+                // @phpstan-ignore-next-line
+                $totals += (float)$itemData->get_total() + (float)$itemData->get_total_tax();
             }
 
             $totals = number_format(abs($totals), 2); // WooCommerce - sum of all refund items
-            $checkAmount = $amount ? number_format((float)$amount, 2) : 0; // WooCommerce - refund amount
+            // phpstan:ignore [wc-stub] $amount arrives via WC refund API as string|null; (float) cast already handles it but stubs type it inconsistently
+            // @phpstan-ignore-next-line
+            $checkAmount = number_format((float)($amount ?? 0), 2); // WooCommerce - refund amount
 
             if ($checkAmount !== $totals) {
                 $errorMessage = _x('The sum of refunds for all order lines is not identical to the refund amount, so this refund will be processed as a payment amount refund, not an order line refund.', 'Order note error', 'mollie-payments-for-woocommerce');
@@ -272,8 +271,6 @@ public function refund(WC_Order $order, $orderId, $paymentObject, $amount = null
             $this->logger->debug(__METHOD__ . ' - ' . $exceptionMessage);
             return new WP_Error(1, $exceptionMessage);
         }
-
-        return false;
     }
 
     /**
@@ -318,6 +315,8 @@ public function refund_order_items($order, $orderId, $amount, $items, $paymentOb
 
                 if ($originalOrderItemId === $line->metadata->order_item_id) {
                     // Calculate the total refund amount for one order line
+                    // phpstan:ignore [mollie-stub] Mollie order line exposes unitPrice->value as a dynamic stdClass property not covered by type definitions
+                    // @phpstan-ignore-next-line
                     $lineTotalRefundAmount = abs($item->get_quantity()) * $line->unitPrice->value;
 
                     // Mollie doesn't allow a partial refund of the full amount or quantity of at least one order line, so when merchants try that, warn them and block the process
@@ -325,6 +324,8 @@ public function refund_order_items($order, $orderId, $amount, $items, $paymentOb
                         $noteMessage = sprintf(
                             "Mollie doesn't allow a partial refund of the full amount or quantity of at least one order line. Use 'Refund amount' instead. The WooCommerce order item ID is %s, Mollie order line ID is %s.",
                             $originalOrderItemId,
+                            // phpstan:ignore [mollie-stub] Mollie order line exposes id as a dynamic property not covered by type definitions
+                            // @phpstan-ignore-next-line
                             $line->id
                         );
 
@@ -386,7 +387,7 @@ public function refund_amount($order, $amount, $paymentObject, $reason)
             throw new Exception(esc_html(sprintf("%s", $noteMessage)));
         }
 
-        if ($paymentObject->isPaid() || $paymentObject->isShipping() || $paymentObject->isCompleted()) {
+        if ($paymentObject->isPaid() || $paymentObject->isCompleted()) {
             $refund = $this->apiHelper->getApiClient($apiKey)->payments->refund($paymentObjectPayment, [
                 'amount' =>  [
                     'currency' => $this->dataHelper->getOrderCurrency($order),
@@ -470,13 +471,15 @@ protected function processOrderItemsRefund(
         // Get the Mollie order
         $mollieOrder = $this->apiHelper->getApiClient($apiKey)->orders->get($paymentObject->id);
 
-        $itemTotalAmount = abs(number_format($item->get_total() + $item->get_total_tax(), 2));
+        $itemTotalAmount = abs((float)number_format($item->get_total() + $item->get_total_tax(), 2));
 
         // Prepare the order line to update
         if (!empty($line->discountAmount)) {
             $lines = [
                 'lines' => [
                     [
+                        // phpstan:ignore [mollie-stub] Mollie order line exposes id as a dynamic property not covered by type definitions
+                        // @phpstan-ignore-next-line
                         'id' => $line->id,
                         'quantity' => abs($item->get_quantity()),
                         'amount' => [
@@ -502,6 +505,8 @@ protected function processOrderItemsRefund(
             ];
         }
 
+        $refund = null;
+        $noteMessage = '';
         if ($line->status === 'created' || $line->status === 'authorized') {
             // Returns null if successful.
             $refund = $mollieOrder->cancelLines($lines);
@@ -563,7 +568,7 @@ protected function processOrderItemsRefund(
             $this->pluginId . '_refund_created',
             [$refund, $order],
             '5.3.1',
-            self::ACTION_AFTER_REFUND_PAYMENT_CREATED
+            MolliePayment::ACTION_AFTER_REFUND_PAYMENT_CREATED
         );
 
         $order->add_order_note($noteMessage);
diff --git a/src/Payment/MollieOrderService.php b/src/Payment/MollieOrderService.php
index 555380c77..1546bd9b9 100644
--- a/src/Payment/MollieOrderService.php
+++ b/src/Payment/MollieOrderService.php
@@ -36,6 +36,8 @@ class MollieOrderService
     protected $data;
     protected $pluginId;
     private ContainerInterface $container;
+    // phpstan:ignore [dead-code] declared but never assigned after construction; likely a concurrency guard placeholder
+    // @phpstan-ignore-next-line
     private string $currentLockValue;
     private WebhookHandler $webhookHandler;
 
@@ -584,6 +586,8 @@ protected function processChargebacks(WC_Order $order, $payment)
                 !empty($emails) && !empty($orderId)
                 && !empty($emails['WC_Email_Failed_Order'])
             ) {
+                // phpstan:ignore [wc-stub] WC_Email subclass accessed via mailer array; trigger() not typed on WC_Email base class in stubs
+                // @phpstan-ignore-next-line
                 $emails['WC_Email_Failed_Order']->trigger($orderId);
             }
 
diff --git a/src/Payment/MolliePayment.php b/src/Payment/MolliePayment.php
index f5641c1fd..e2f91ded7 100644
--- a/src/Payment/MolliePayment.php
+++ b/src/Payment/MolliePayment.php
@@ -4,20 +4,15 @@
 
 namespace Mollie\WooCommerce\Payment;
 
-use Inpsyde\PaymentGateway\PaymentGateway;
 use Mollie\Api\Exceptions\ApiException;
 use Mollie\Api\Resources\Payment;
 use Mollie\Api\Resources\Refund;
 use Mollie\WooCommerce\Payment\Request\RequestFactory;
-use Mollie\WooCommerce\PaymentMethods\Voucher;
 use Mollie\WooCommerce\SDK\Api;
 use Mollie\WooCommerce\Settings\Settings;
 use Mollie\WooCommerce\Shared\Data;
-use Mollie\WooCommerce\Shared\SharedDataDictionary;
 use Psr\Log\LoggerInterface as Logger;
-use Psr\Log\LogLevel;
 use WC_Order;
-use WC_Subscriptions_Manager;
 use WP_Error;
 
 class MolliePayment extends MollieObject
@@ -74,9 +69,6 @@ public function getPaymentRequestData($order, $customerId)
         return $this->requestFactory->createRequest('payment', $order, $customerId);
     }
 
-    /**
-     * @return void
-     */
     public function setActiveMolliePayment($orderId)
     {
         self::$paymentId = $this->getMolliePaymentIdFromPaymentObject();
@@ -87,6 +79,7 @@ public function setActiveMolliePayment($orderId)
         self::$order->save();
 
         parent::setActiveMolliePayment($orderId);
+        return $this;
     }
 
     public function getMolliePaymentIdFromPaymentObject()
diff --git a/src/Payment/MollieSubscription.php b/src/Payment/MollieSubscription.php
index db787150f..1807603ea 100644
--- a/src/Payment/MollieSubscription.php
+++ b/src/Payment/MollieSubscription.php
@@ -5,7 +5,7 @@
 use Mollie\Api\Types\SequenceType;
 use Mollie\WooCommerce\Payment\Request\Middleware\MiddlewareHandler;
 use Mollie\WooCommerce\Payment\Request\Middleware\PaymentDescriptionMiddleware;
-use Mollie\WooCommerce\PaymentMethods\AbstractPaymentMethod;
+use Mollie\WooCommerce\PaymentMethods\PaymentMethodI;
 use Mollie\WooCommerce\SDK\Api;
 use Mollie\WooCommerce\Subscription\MollieSubscriptionGatewayHandler;
 use Psr\Log\LoggerInterface as Logger;
@@ -13,18 +13,25 @@
 class MollieSubscription extends MollieObject
 {
     protected $pluginId;
-    /**
-     * @var mixed
-     */
-    private AbstractPaymentMethod $paymentMethod;
+    // phpstan:ignore [dead-code] injected via constructor but never read in this class; MollieObject subclasses access it through other paths
+    // @phpstan-ignore-next-line
+    private PaymentMethodI $paymentMethod;
     protected MiddlewareHandler $middleware;
 
     /**
      * Molliesubscription constructor.
      *
      */
-    public function __construct($pluginId, Api $apiHelper, $settingsHelper, $dataHelper, Logger $logger, AbstractPaymentMethod $paymentMethod, $middlewareHandler)
-    {
+    public function __construct(
+        $pluginId,
+        Api $apiHelper,
+        $settingsHelper,
+        $dataHelper,
+        Logger $logger,
+        PaymentMethodI $paymentMethod,
+        $middlewareHandler
+    ) {
+
         $this->pluginId = $pluginId;
         $this->apiHelper = $apiHelper;
         $this->settingsHelper = $settingsHelper;
diff --git a/src/Payment/PaymentModule.php b/src/Payment/PaymentModule.php
index 82d765d17..3e7b8f74e 100644
--- a/src/Payment/PaymentModule.php
+++ b/src/Payment/PaymentModule.php
@@ -114,7 +114,7 @@ function () use ($paymentMethods) {
                 $this->handleExpiryDateCancelation($paymentMethods);
             },
             10,
-            2
+            0
         );
         add_action(
             OrderItemsRefunder::ACTION_AFTER_REFUND_ORDER_ITEMS,
@@ -165,7 +165,7 @@ public function cancelOrderOnExpiryDate()
                 continue;
             }
 
-            $heldDuration = isset($gatewaySettings) && isset($gatewaySettings['order_dueDate']) ? $gatewaySettings['order_dueDate'] : 0;
+            $heldDuration = isset($gatewaySettings['order_dueDate']) ? $gatewaySettings['order_dueDate'] : 0;
 
             if ($heldDuration < 1) {
                 continue;
@@ -530,7 +530,7 @@ public function handleExpiryDateCancelation($paymentMethods)
                 'mollie_woocommerce_cancel_unpaid_orders',
                 [$this, 'cancelOrderOnExpiryDate'],
                 11,
-                2
+                0
             );
         }
     }
diff --git a/src/Payment/PaymentProcessor.php b/src/Payment/PaymentProcessor.php
index 4e38b5d28..a4fbc42be 100644
--- a/src/Payment/PaymentProcessor.php
+++ b/src/Payment/PaymentProcessor.php
@@ -9,12 +9,12 @@
 use Mollie\Api\Exceptions\ApiException;
 use Mollie\Api\Resources\Payment;
 use Mollie\WooCommerce\Notice\NoticeInterface;
+use Mollie\WooCommerce\PaymentMethods\Constants;
 use Mollie\WooCommerce\PaymentMethods\PaymentMethodI;
 use Mollie\WooCommerce\SDK\Api;
 use Mollie\WooCommerce\Settings\Settings;
 use Mollie\WooCommerce\Shared\Data;
 use Mollie\WooCommerce\Shared\SharedDataDictionary;
-use Mollie\WooCommerce\PaymentMethods\Constants;
 use Psr\Log\LoggerInterface as Logger;
 use WC_Order;
 
@@ -24,7 +24,7 @@ class PaymentProcessor implements PaymentProcessorInterface
     public const PAYMENT_METHOD_TYPE_PAYMENT = 'payment';
 
     /**
-     * @var
+     * @var mixed
      */
     protected $deprecatedGatewayHelper;
     /**
diff --git a/src/Payment/Request/Middleware/AddSequenceTypeForSubscriptionsMiddleware.php b/src/Payment/Request/Middleware/AddSequenceTypeForSubscriptionsMiddleware.php
index 12b686c8c..bbf7a9f64 100644
--- a/src/Payment/Request/Middleware/AddSequenceTypeForSubscriptionsMiddleware.php
+++ b/src/Payment/Request/Middleware/AddSequenceTypeForSubscriptionsMiddleware.php
@@ -7,6 +7,7 @@
 use Mollie\Api\Types\SequenceType;
 use Mollie\WooCommerce\Shared\Data;
 use WC_Order;
+use WC_Payment_Gateway;
 
 /**
  * Middleware to add sequence type for subscription payments.
@@ -47,7 +48,7 @@ public function __construct($dataHelper, $pluginId)
     public function __invoke(array $requestData, WC_Order $order, $context, callable $next): array
     {
         $gateway = wc_get_payment_gateway_by_order($order);
-        if ($gateway) {
+        if ($gateway instanceof WC_Payment_Gateway) {
             $requestData = $this->addSequenceTypeForSubscriptionsFirstPayments($order->get_id(), $gateway, $requestData, $context);
         }
         return $next($requestData, $order, $context);
diff --git a/src/Payment/Request/Middleware/CustomerBirthdateMiddleware.php b/src/Payment/Request/Middleware/CustomerBirthdateMiddleware.php
index a74f37c04..f7cc3424f 100644
--- a/src/Payment/Request/Middleware/CustomerBirthdateMiddleware.php
+++ b/src/Payment/Request/Middleware/CustomerBirthdateMiddleware.php
@@ -2,8 +2,8 @@
 
 namespace Mollie\WooCommerce\Payment\Request\Middleware;
 
-use WC_Order;
 use Mollie\WooCommerce\Shared\FieldConstants;
+use WC_Order;
 
 /**
  * Middleware to handle customer birthdate in the request.
@@ -13,6 +13,8 @@ class CustomerBirthdateMiddleware implements RequestMiddlewareInterface
     /**
      * @var array The payment methods.
      */
+    // phpstan:ignore [dead-code] injected via constructor but never read; likely needed once birthdate validation checks which methods require it
+    // @phpstan-ignore-next-line
     private array $paymentMethods;
 
     /**
@@ -37,7 +39,7 @@ public function __construct(array $paymentMethods)
     public function __invoke(array $requestData, WC_Order $order, $context, $next): array
     {
         $birthdatePostedFieldName = $this->getBirthdatePostedFieldName($order);
-        if (!$birthdatePostedFieldName || $birthdatePostedFieldName === '' || !is_string($birthdatePostedFieldName)) {
+        if (!$birthdatePostedFieldName) {
             return $next($requestData, $order, $context);
         }
         $format = "Y-m-d";
diff --git a/src/Payment/Webhooks/WebhookHandler.php b/src/Payment/Webhooks/WebhookHandler.php
index 7ff54f6e6..3ae95bd6a 100644
--- a/src/Payment/Webhooks/WebhookHandler.php
+++ b/src/Payment/Webhooks/WebhookHandler.php
@@ -270,6 +270,7 @@ public function onWebhookCanceled(
         $mollieObject->setCancelledMolliePaymentId($orderId, $payment->id);
 
         $orderStatusCancelledPayments = $this->settingsHelper->getOrderStatusCancelledPayments();
+        $newOrderStatus = SharedDataDictionary::STATUS_PENDING;
 
         if ($orderStatusCancelledPayments === 'pending' || $orderStatusCancelledPayments === null) {
             $newOrderStatus = SharedDataDictionary::STATUS_PENDING;
diff --git a/src/PaymentMethods/AbstractPaymentMethod.php b/src/PaymentMethods/AbstractPaymentMethod.php
index f6f5071c5..effe1251c 100644
--- a/src/PaymentMethods/AbstractPaymentMethod.php
+++ b/src/PaymentMethods/AbstractPaymentMethod.php
@@ -57,6 +57,18 @@ abstract class AbstractPaymentMethod implements PaymentMethodI, PaymentMethodDef
      */
     protected bool $translationsInitialized = false;
 
+    abstract protected function getConfig(): array;
+
+    abstract public function getFormFields(array $generalFormFields): array;
+
+    public function filtersOnBuild(): void
+    {
+    }
+
+    public function debugGiftcardDetails($payment, \WC_Order $order): void
+    {
+    }
+
     public function __construct()
     {
         $this->config = $this->getConfig();
@@ -477,6 +489,8 @@ public function blocksData(ContainerInterface $container): array
             ], $iconProvider->provideIcons())
             : [];
 
+        // phpstan:ignore [wc-stub] WC()->customer is WC_Customer|null at runtime; WooCommerce stubs declare it non-nullable
+        // @phpstan-ignore-next-line
         $billingCountry = WC()->customer ? WC()->customer->get_billing_country() : '';
         $allowedCountries = $this->getProperty('allowed_countries');
 
diff --git a/src/PaymentMethods/Banktransfer.php b/src/PaymentMethods/Banktransfer.php
index 5f21cc38b..be376b5e1 100644
--- a/src/PaymentMethods/Banktransfer.php
+++ b/src/PaymentMethods/Banktransfer.php
@@ -90,7 +90,7 @@ public function getFormFields($generalFormFields): array
         return array_merge($generalFormFields, $paymentMethodFormFieds);
     }
 
-    public function filtersOnBuild()
+    public function filtersOnBuild(): void
     {
         add_filter('woocommerce_mollie_wc_gateway_' . $this->getProperty('id') . 'payment_args', function (array $args, \WC_Order $order): array {
             return $this->addPaymentArguments($args, $order);
diff --git a/src/PaymentMethods/Billie.php b/src/PaymentMethods/Billie.php
index 18b1e85f3..a2e5072d3 100644
--- a/src/PaymentMethods/Billie.php
+++ b/src/PaymentMethods/Billie.php
@@ -65,7 +65,7 @@ public function initializeTranslations(): void
      * Add filters and actions for the Billie payment method.
      * This will be added during constructor
      */
-    public function filtersOnBuild()
+    public function filtersOnBuild(): void
     {
         add_filter(
             'woocommerce_after_checkout_validation',
@@ -73,7 +73,7 @@ public function filtersOnBuild()
             11,
             2
         );
-        add_action(
+        add_filter(
             'woocommerce_checkout_posted_data',
             [$this, 'switchFields'],
             11
diff --git a/src/PaymentMethods/Giftcard.php b/src/PaymentMethods/Giftcard.php
index bced341f4..8d1490522 100644
--- a/src/PaymentMethods/Giftcard.php
+++ b/src/PaymentMethods/Giftcard.php
@@ -18,7 +18,7 @@ class Giftcard extends AbstractPaymentMethod implements PaymentMethodI
     public function debugGiftcardDetails(
         $payment,
         \WC_Order $order
-    ) {
+    ): void {
 
         $details = $payment->details;
         if (!$details) {
diff --git a/src/PaymentMethods/Paybybank.php b/src/PaymentMethods/Paybybank.php
index 2f9a11f14..bd6a777ec 100644
--- a/src/PaymentMethods/Paybybank.php
+++ b/src/PaymentMethods/Paybybank.php
@@ -88,7 +88,7 @@ public function getFormFields(array $generalFormFields): array
         return array_merge($generalFormFields, $paymentMethodFormFields);
     }
 
-    public function filtersOnBuild()
+    public function filtersOnBuild(): void
     {
         add_filter('woocommerce_mollie_wc_gateway_' . $this->getProperty('id') . 'payment_args', function (array $args, \WC_Order $order): array {
             return $this->addPaymentArguments($args, $order);
diff --git a/src/PaymentMethods/PaymentFieldsStrategies/AbstractPaymentFieldsRenderer.php b/src/PaymentMethods/PaymentFieldsStrategies/AbstractPaymentFieldsRenderer.php
index e42ae8e03..f70c2a76f 100644
--- a/src/PaymentMethods/PaymentFieldsStrategies/AbstractPaymentFieldsRenderer.php
+++ b/src/PaymentMethods/PaymentFieldsStrategies/AbstractPaymentFieldsRenderer.php
@@ -11,9 +11,6 @@ class AbstractPaymentFieldsRenderer implements PaymentFieldsRendererInterface
     protected MolliePaymentGatewayHandler $deprecatedHelperGateway;
 
     protected string $gatewayDescription;
-    /**
-     * @var mixed
-     */
     protected Data $dataHelper;
 
     public function __construct($deprecatedHelperGateway, $gateway, $dataHelper)
diff --git a/src/PaymentMethods/PaymentFieldsStrategies/IssuersDropdownBehavior.php b/src/PaymentMethods/PaymentFieldsStrategies/IssuersDropdownBehavior.php
index 26f2638b6..6586650b2 100644
--- a/src/PaymentMethods/PaymentFieldsStrategies/IssuersDropdownBehavior.php
+++ b/src/PaymentMethods/PaymentFieldsStrategies/IssuersDropdownBehavior.php
@@ -80,8 +80,7 @@ public function issuersDropdownMarkup(
     }
 
     /**
-     * @param        $description
-     * @param string $html
+     * @param        $gateway
      * @param        $issuers
      * @param        $selectedIssuer
      *
diff --git a/src/PaymentMethods/PaymentMethodI.php b/src/PaymentMethods/PaymentMethodI.php
index a6bf5b514..a44e3ee43 100644
--- a/src/PaymentMethods/PaymentMethodI.php
+++ b/src/PaymentMethods/PaymentMethodI.php
@@ -12,4 +12,18 @@ public function getProperty(string $propertyName);
     public function hasProperty(string $propertyName): bool;
 
     public function blocksData(ContainerInterface $container): array;
+
+    public function shouldDisplayIcon(): bool;
+
+    public function id(): string;
+
+    public function initializeTranslations(): void;
+
+    public function updateSettingsWithDefaults(ContainerInterface $container): array;
+
+    public function getInitialOrderStatus(): string;
+
+    public function filtersOnBuild(): void;
+
+    public function debugGiftcardDetails($payment, \WC_Order $order): void;
 }
diff --git a/src/PaymentMethods/PaymentRedirectStrategies/DefaultRedirectStrategy.php b/src/PaymentMethods/PaymentRedirectStrategies/DefaultRedirectStrategy.php
index 1efbdc90e..ec414d22f 100644
--- a/src/PaymentMethods/PaymentRedirectStrategies/DefaultRedirectStrategy.php
+++ b/src/PaymentMethods/PaymentRedirectStrategies/DefaultRedirectStrategy.php
@@ -4,8 +4,8 @@
 
 namespace Mollie\WooCommerce\PaymentMethods\PaymentRedirectStrategies;
 
-use Mollie\WooCommerce\Payment\MollieOrder;
-use Mollie\WooCommerce\Payment\MolliePayment;
+use Mollie\Api\Resources\Order as MollieApiOrder;
+use Mollie\Api\Resources\Payment as MollieApiPayment;
 use Mollie\WooCommerce\PaymentMethods\PaymentMethodI;
 use WC_Order;
 
@@ -15,11 +15,11 @@ class DefaultRedirectStrategy implements PaymentRedirectStrategyI
      * Redirect location after successfully completing process_payment
      *
      * @param WC_Order $order
-     * @param MollieOrder|MolliePayment $payment_object
+     * @param MollieApiOrder|MollieApiPayment $paymentObject
      *
      */
     public function execute(PaymentMethodI $paymentMethod, $order, $paymentObject, string $redirectUrl)
     {
-            return $paymentObject->getCheckoutUrl();
+        return $paymentObject->getCheckoutUrl();
     }
 }
diff --git a/src/PaymentMethods/Voucher.php b/src/PaymentMethods/Voucher.php
index b43ad714a..40a7c6dde 100644
--- a/src/PaymentMethods/Voucher.php
+++ b/src/PaymentMethods/Voucher.php
@@ -4,9 +4,6 @@
 
 namespace Mollie\WooCommerce\PaymentMethods;
 
-use Mollie\WooCommerce\Payment\MollieOrder;
-use Mollie\WooCommerce\Payment\MolliePayment;
-
 class Voucher extends AbstractPaymentMethod implements PaymentMethodI
 {
     /**
@@ -54,9 +51,8 @@ protected function getConfig(): array
         ];
     }
 
-    public function filtersOnBuild()
+    public function filtersOnBuild(): void
     {
-
         add_action('mollie-payments-for-woocommerce_after_webhook_action', [$this, 'addPaymentDetailsOrderNote'], 10, 2);
     }
 
@@ -93,6 +89,8 @@ public function addPaymentDetailsOrderNote($payment, \WC_Order $order): void
         if (isset($details->remainderAmount)) {
             $remainder = sprintf(
                 __('%1$s: %2$s %3$s<br/>', 'mollie-payments-for-woocommerce'),
+                // phpstan:ignore [mollie-stub] Mollie payment detail object exposes remainderMethod as a dynamic property not covered by type definitions
+                // @phpstan-ignore-next-line
                 $details->remainderMethod,
                 $details->remainderAmount->value,
                 $details->remainderAmount->currency
diff --git a/src/SDK/Api.php b/src/SDK/Api.php
index 861aee416..47d767cce 100644
--- a/src/SDK/Api.php
+++ b/src/SDK/Api.php
@@ -10,9 +10,9 @@
 class Api
 {
     /**
-     * @var \Mollie\Api\MollieApiClient
+     * @var \Mollie\Api\MollieApiClient|null
      */
-    protected static $api_client;
+    protected static ?MollieApiClient $api_client = null;
     /**
      * @var string
      */
@@ -29,7 +29,7 @@ public function __construct(string $pluginVersion, string $pluginId)
     }
 
     /**
-     * @param bool $test_mode
+     * @param string $apiKey
      * @param bool $needToUpdateApiKey If the apiKey was updated discard the old instance, and create a new one with the new key.
      *
      * @return \Mollie\Api\MollieApiClient
@@ -59,7 +59,7 @@ public function getApiClient($apiKey, $needToUpdateApiKey = false)
             );
         }
 
-        if (empty(self::$api_client) || $needToUpdateApiKey) {
+        if (self::$api_client === null || $needToUpdateApiKey) {
             $client = new MollieApiClient(null, new WordPressHttpAdapterPicker());
             $client->setApiKey($apiKey);
             $client->setApiEndpoint($this->getApiEndpoint());
diff --git a/src/SDK/WordPressHttpAdapter.php b/src/SDK/WordPressHttpAdapter.php
index 53aa5825d..6985d76c4 100644
--- a/src/SDK/WordPressHttpAdapter.php
+++ b/src/SDK/WordPressHttpAdapter.php
@@ -5,7 +5,6 @@
 namespace Mollie\WooCommerce\SDK;
 
 use Mollie\Api\Exceptions\ApiException;
-use Mollie\Api\Exceptions\CurlConnectTimeoutException;
 use Mollie\Api\HttpAdapter\MollieHttpAdapterInterface;
 
 class WordPressHttpAdapter implements MollieHttpAdapterInterface
@@ -43,7 +42,7 @@ public function send($httpMethod, $url, $headers, $httpBody)
         $response = wp_remote_request($url, $args);
 
         if (is_wp_error($response)) {
-            $message =  $response->get_error_message() ?? 'Unknown error';
+            $message = $response->get_error_message();
             $code = is_int($response->get_error_code()) ? $response->get_error_code() : 0;
             // phpcs:disable WordPress.Security.EscapeOutput.ExceptionNotEscaped
             throw new ApiException(esc_html($message), $code);
@@ -99,9 +98,7 @@ protected function parseResponse($response)
                 $message .= ". Documentation: {$body->_links->documentation->href}";
             }
 
-            if ($httpBody) {
-                $message .= ". Request body: {$httpBody}";
-            }
+            $message .= ". Request body: {$httpBody}";
             // phpcs:disable WordPress.Security.EscapeOutput.ExceptionNotEscaped
             throw new ApiException(esc_html($message), $statusCode, esc_html($field));
             // phpcs:enable WordPress.Security.EscapeOutput.ExceptionNotEscaped
diff --git a/src/SDK/WordPressHttpAdapterPicker.php b/src/SDK/WordPressHttpAdapterPicker.php
index 20683c55d..438a52861 100644
--- a/src/SDK/WordPressHttpAdapterPicker.php
+++ b/src/SDK/WordPressHttpAdapterPicker.php
@@ -9,7 +9,8 @@
 class WordPressHttpAdapterPicker implements MollieHttpAdapterPickerInterface
 {
     /**
-     * @return \GuzzleHttp\ClientInterface|\Mollie\Api\HttpAdapter\MollieHttpAdapterInterface
+     * @param mixed $httpClient
+     * @return \Mollie\Api\HttpAdapter\MollieHttpAdapterInterface
      */
     public function pickHttpAdapter($httpClient)
     {
diff --git a/src/Settings/General/MultiCountrySettingsField.php b/src/Settings/General/MultiCountrySettingsField.php
index d919e0b79..fcf9b40e3 100644
--- a/src/Settings/General/MultiCountrySettingsField.php
+++ b/src/Settings/General/MultiCountrySettingsField.php
@@ -28,6 +28,8 @@ public function multiSelectCountry($paymentMethod)
         $gatewayId = $paymentMethod->getProperty('id');
         $id = 'woocommerce_mollie_wc_gateway_' . $gatewayId . '_allowed_countries';
         $title = __('Sell to specific countries', 'mollie-payments-for-woocommerce');
+        // phpstan:ignore [wc-stub] WC()->countries is WC_Countries|null at runtime; WooCommerce stubs declare it non-nullable
+        // @phpstan-ignore-next-line
         $countries = WC()->countries->countries;
         asort($countries);
         ob_start();
diff --git a/src/Settings/Page/Section/PaymentMethods.php b/src/Settings/Page/Section/PaymentMethods.php
index bdf1cbba8..ecf46567d 100644
--- a/src/Settings/Page/Section/PaymentMethods.php
+++ b/src/Settings/Page/Section/PaymentMethods.php
@@ -54,7 +54,7 @@ public function renderGateways(): string
         $activatedGateways = '';
         $deactivatedGateways = '';
 
-        /** @var AbstractPaymentMethod $paymentMethod */
+        /** @var AbstractPaymentMethod[] $paymentMethods */
         $paymentMethods = $this->container->get('gateway.paymentMethods');
         $enabledMethods =  $this->container->get('gateway.paymentMethodsEnabledAtMollie');
         if (!in_array(Constants::DIRECTDEBIT, $enabledMethods, true)) {
@@ -200,7 +200,7 @@ protected function paymentGatewayButton(AbstractPaymentMethod $paymentMethod, $e
                 'enabled',
                 'mollie-payments-for-woocommerce'
             )) . '</span>';
-        } elseif ($enabledInMollie && !$enabledInWoo) {
+        } elseif (!$enabledInWoo) {
             $messageOrLink = '<span class="mollie-settings-pm__status mollie-settings-pm__status--disabled">' . esc_html(__(
                 'disabled',
                 'mollie-payments-for-woocommerce'
diff --git a/src/Settings/Settings.php b/src/Settings/Settings.php
index 417413015..8928751b6 100644
--- a/src/Settings/Settings.php
+++ b/src/Settings/Settings.php
@@ -169,13 +169,13 @@ public function isOrderApiSetting()
         return !$orderApiSetting || is_string($orderApiSetting) && trim($orderApiSetting) === PaymentProcessor::PAYMENT_METHOD_TYPE_ORDER;
     }
     /**
-     * @param bool $overrideTestMode
+     * @param bool|null $overrideTestMode Pass null to use the current test mode setting.
      *
      * @return false|string
      */
-    public function getApiKey($overrideTestMode = 2)
+    public function getApiKey(?bool $overrideTestMode = null)
     {
-        $isTestModeEnabled = $overrideTestMode === 2 ? $this->isTestModeEnabled() : $overrideTestMode;
+        $isTestModeEnabled = $overrideTestMode === null ? $this->isTestModeEnabled() : $overrideTestMode;
         $settingId = $isTestModeEnabled ? 'test_api_key' : 'live_api_key';
         $apiKeyId = $this->getSettingId($settingId);
         $apiKey = get_option($apiKeyId);
@@ -418,7 +418,15 @@ public function getSettingId($setting)
         $max_option_name_length = 191;
 
         if ($setting_id_length > $max_option_name_length) {
-            trigger_error(sprintf('Setting id %s (%s) to long for database column wp_options.option_name which is varchar(%s).', esc_html($setting_id), esc_html($setting_id_length), esc_html($max_option_name_length)), E_USER_WARNING);
+            trigger_error(
+                sprintf(
+                    'Setting id %s (%s) to long for database column wp_options.option_name which is varchar(%s).',
+                    esc_html($setting_id),
+                    esc_html((string)$setting_id_length),
+                    esc_html((string)$max_option_name_length)
+                ),
+                E_USER_WARNING
+            );
         }
 
         return $setting_id;
@@ -541,7 +549,7 @@ protected function updateGatewaySettings($gateway)
      * If we are calling this the api key has been updated, we need a new api object
      * to retrieve a new profile id
      *
-     * @return CurrentProfile
+     * @return \Mollie\Api\Resources\CurrentProfile
      * @throws ApiException
      */
     protected function mollieWooCommerceMerchantProfile()
@@ -575,7 +583,7 @@ public function mollieWooCommerceMerchantProfileId()
             if (!$merchantProfileId) {
                 try {
                     $merchantProfile = $this->mollieWooCommerceMerchantProfile();
-                    $merchantProfileId = isset($merchantProfile->id) ? $merchantProfile->id : '';
+                    $merchantProfileId = $merchantProfile->id;
                 } catch (ApiException $exception) {
                     $merchantProfileId = '';
                 }
diff --git a/src/Settings/SettingsModule.php b/src/Settings/SettingsModule.php
index 3c1f3a1b0..a73d08536 100644
--- a/src/Settings/SettingsModule.php
+++ b/src/Settings/SettingsModule.php
@@ -6,16 +6,15 @@
 
 namespace Mollie\WooCommerce\Settings;
 
+use Inpsyde\Modularity\Module\ExecutableModule;
+use Inpsyde\Modularity\Module\ModuleClassNameIdTrait;
+use Inpsyde\Modularity\Module\ServiceModule;
 use Mollie\WooCommerce\Notice\AdminNotice;
-use Mollie\WooCommerce\PaymentMethods\Constants;
 use Mollie\WooCommerce\SDK\Api;
 use Mollie\WooCommerce\Settings\Webhooks\WebhookTestService;
 use Mollie\WooCommerce\Shared\Data;
 use Mollie\WooCommerce\Shared\Status;
 use Mollie\WooCommerce\Uninstall\CleanDb;
-use Inpsyde\Modularity\Module\ExecutableModule;
-use Inpsyde\Modularity\Module\ModuleClassNameIdTrait;
-use Inpsyde\Modularity\Module\ServiceModule;
 use Psr\Container\ContainerInterface;
 use Psr\Log\LoggerInterface as Logger;
 
@@ -178,7 +177,7 @@ function () use ($optionName, $defaultAdvancedOptions, $defaultComponentsOptions
                 $this->maybeSaveDefaultSettings('mollie_components_', $testedOption, $defaultComponentsOptions);
             },
             10,
-            2
+            0
         );
         $this->isTestNoticePrinted = false;
         add_action('woocommerce_settings_saved', function () {
diff --git a/src/Shared/Data.php b/src/Shared/Data.php
index 4387c30de..0c9290dbf 100644
--- a/src/Shared/Data.php
+++ b/src/Shared/Data.php
@@ -7,11 +7,9 @@
 use Exception;
 use InvalidArgumentException;
 use Mollie\Api\Resources\Method;
-use Mollie\WooCommerce\Buttons\ApplePayButton\DataToAppleButtonScripts;
 use Mollie\WooCommerce\SDK\Api;
 use Mollie\WooCommerce\Settings\Settings;
 use Psr\Log\LoggerInterface as Logger;
-use Psr\Log\LogLevel;
 use WC_Customer;
 use WC_Order;
 
@@ -111,11 +109,11 @@ public function isTestModeEnabled(): bool
     }
 
     /**
-     * @param bool $overrideTestMode
+     * @param bool|null $overrideTestMode Pass null to use the current test mode setting.
      *
      * @return false|string
      */
-    public function getApiKey($overrideTestMode = 2)
+    public function getApiKey(?bool $overrideTestMode = null)
     {
         return $this->settingsHelper->getApiKey($overrideTestMode);
     }
@@ -160,7 +158,16 @@ public function getTransientId($transient)
         $max_option_name_length = 191;
 
         if ($option_name_length > $max_option_name_length) {
-            trigger_error(sprintf('Transient id %s is to long. Option name %s (%s) will be to long for database column wp_options.option_name which is varchar(%s).', esc_html($transient_id), esc_html($option_name), esc_html($option_name_length), esc_html($max_option_name_length)), E_USER_WARNING);
+            trigger_error(
+                sprintf(
+                    'Transient id %s is to long. Option name %s (%s) will be to long for database column wp_options.option_name which is varchar(%s).',
+                    esc_html($transient_id),
+                    esc_html($option_name),
+                    esc_html((string)$option_name_length),
+                    esc_html((string)$max_option_name_length)
+                ),
+                E_USER_WARNING
+            );
         }
 
         return $transient_id;
@@ -212,9 +219,13 @@ public function wooCommerceFiltersForCheckout(): array
     {
 
         $cart = WC()->cart;
+        // phpstan:ignore [wc-stub] WC()->cart is WC_Cart|null at runtime; WooCommerce stubs declare it non-nullable
+        // @phpstan-ignore-next-line
         $cartTotal = $cart ? $cart->get_total('edit') : 0;
 
         $currency = get_woocommerce_currency();
+        // phpstan:ignore [wc-stub] WC()->customer is WC_Customer|null at runtime; WooCommerce stubs declare it non-nullable
+        // @phpstan-ignore-next-line
         $customerExistsAndHasCountry = WC()->customer && !empty(WC()->customer->get_billing_country());
         $fallbackToShopCountry = wc_get_base_location()['country'];
         $billingCountry = $customerExistsAndHasCountry ? WC()->customer->get_billing_country() : $fallbackToShopCountry;
@@ -324,7 +335,7 @@ public function getRegularPaymentMethods($apiKey, $testMode = false, $useCache =
         $methods = $this->getAllAvailablePaymentMethods($useCache);
         // We cannot access allActive for all methods so we filter them out here
         $filtered_methods = array_filter($methods, static function ($method) use ($testMode) {
-            if ($testMode === "live") {
+            if (!$testMode) {
                 return $method['status'] === "activated";
             } else {
                 return in_array($method['status'], ["activated", "pending-review"]);
@@ -409,7 +420,6 @@ public function getApiPaymentMethods($useCache = true, $filters = [])
     }
 
     /**
-     * @param bool $testMode
      * @param      $method
      *
      * @return mixed|\Mollie\Api\Resources\Method|null
@@ -550,8 +560,8 @@ public function setUserMollieCustomerIdAtSubscription($orderId, $customerId)
     }
 
     /**
-     * @param int  $userId
-     * @param bool $testMode
+     * @param int $userId
+     * @param string $apiKey
      * @return null|string
      */
     public function getUserMollieCustomerId($userId, $apiKey)
@@ -601,7 +611,7 @@ public function getUserMollieCustomerId($userId, $apiKey)
                 // Get the best name for use as Mollie Customer name
                 $user_full_name = $userdata->first_name . ' ' . $userdata->last_name;
 
-                if (strlen(trim($user_full_name)) === null) {
+                if (strlen(trim($user_full_name)) === 0) {
                     $user_full_name = $userdata->display_name;
                 }
 
diff --git a/src/Shared/GatewaySurchargeHandler.php b/src/Shared/GatewaySurchargeHandler.php
index 8a408de44..91a5ef467 100644
--- a/src/Shared/GatewaySurchargeHandler.php
+++ b/src/Shared/GatewaySurchargeHandler.php
@@ -120,7 +120,6 @@ public function updateSurchargeOrderPay()
                 'newTotal' => $order->get_total(),
             ];
             wp_send_json_success($data);
-            return;
         }
 
         $amount = $this->surcharge->calculateFeeAmountOrder($order, $gatewaySettings);
diff --git a/src/Subscription/MollieSepaRecurringGatewayHandler.php b/src/Subscription/MollieSepaRecurringGatewayHandler.php
index 04905a9f5..07c78b611 100644
--- a/src/Subscription/MollieSepaRecurringGatewayHandler.php
+++ b/src/Subscription/MollieSepaRecurringGatewayHandler.php
@@ -9,12 +9,10 @@
 use Mollie\Api\Exceptions\ApiException;
 use Mollie\Api\Resources\Payment;
 use Mollie\Api\Types\SequenceType;
-use Mollie\WooCommerce\Gateway\MolliePaymentGatewayHandler;
 use Mollie\WooCommerce\Notice\NoticeInterface;
 use Mollie\WooCommerce\Payment\MollieObject;
 use Mollie\WooCommerce\Payment\MollieOrderService;
 use Mollie\WooCommerce\Payment\PaymentFactory;
-use Mollie\WooCommerce\Payment\PaymentProcessor;
 use Mollie\WooCommerce\PaymentMethods\InstructionStrategies\OrderInstructionsManager;
 use Mollie\WooCommerce\PaymentMethods\PaymentMethodI;
 use Mollie\WooCommerce\SDK\Api;
@@ -67,7 +65,6 @@ public function __construct(
         if (isset($directDebitSettings['enabled']) && $directDebitSettings['enabled'] === 'yes') {
             $this->recurringMollieMethod = $directDebitPaymentMethod;
         }
-        return $this;
     }
 
     /**
@@ -182,7 +179,11 @@ public function handlePaidOrderWebhook($order, $payment)
         ) {
             $payment_method_title = $this->getPaymentMethodTitle($payment);
 
+            // phpstan:ignore [mollie-stub] Mollie Payment object exposes mode and id as dynamic stdClass properties not covered by type definitions
+            // @phpstan-ignore-next-line
             $isTestMode = $payment->mode === 'test';
+            // phpstan:ignore [mollie-stub] see above — $payment->id is also a dynamic property on the same object
+            // @phpstan-ignore-next-line
             $paymentMessage = $payment->id . (
                 $isTestMode
                     ? (' - ' . __('test mode', 'mollie-payments-for-woocommerce'))
diff --git a/src/Subscription/MollieSubscriptionGatewayHandler.php b/src/Subscription/MollieSubscriptionGatewayHandler.php
index 6198655d8..88c00b1b3 100644
--- a/src/Subscription/MollieSubscriptionGatewayHandler.php
+++ b/src/Subscription/MollieSubscriptionGatewayHandler.php
@@ -7,15 +7,16 @@
 use Exception;
 use Mollie\Api\Exceptions\ApiException;
 use Mollie\WooCommerce\Gateway\MolliePaymentGatewayHandler;
+use Mollie\WooCommerce\Notice\NoticeInterface;
 use Mollie\WooCommerce\Payment\MollieObject;
+use Mollie\WooCommerce\Payment\MollieOrderService;
 use Mollie\WooCommerce\Payment\MollieSubscription;
 use Mollie\WooCommerce\Payment\PaymentFactory;
 use Mollie\WooCommerce\Payment\PaymentProcessor;
-use Mollie\WooCommerce\Notice\NoticeInterface;
-use Mollie\WooCommerce\Payment\MollieOrderService;
 use Mollie\WooCommerce\Payment\Request\Middleware\MiddlewareHandler;
 use Mollie\WooCommerce\Payment\Request\Middleware\SelectedIssuerMiddleware;
 use Mollie\WooCommerce\Payment\Request\Middleware\UrlMiddleware;
+use Mollie\WooCommerce\PaymentMethods\Constants;
 use Mollie\WooCommerce\PaymentMethods\InstructionStrategies\OrderInstructionsManager;
 use Mollie\WooCommerce\PaymentMethods\PaymentMethodI;
 use Mollie\WooCommerce\SDK\Api;
@@ -25,7 +26,6 @@
 use Mollie\WooCommerce\Shared\Data;
 use Mollie\WooCommerce\Shared\SharedDataDictionary;
 use Psr\Log\LoggerInterface as Logger;
-use Mollie\WooCommerce\PaymentMethods\Constants;
 use WC_Order;
 
 class MollieSubscriptionGatewayHandler extends MolliePaymentGatewayHandler
@@ -108,7 +108,7 @@ function ($renewal_total, WC_Order $renewal_order) use ($gateway) {
                     $this->scheduled_subscription_payment($renewal_total, $renewal_order, $gateway);
                 },
                 10,
-                3
+                2
             );
 
             // A resubscribe order to record a customer resubscribing to an expired or cancelled subscription.
@@ -125,7 +125,7 @@ function ($payment_meta, $subscription) use ($gateway) {
                     return $this->add_subscription_payment_meta($payment_meta, $subscription, $gateway);
                 },
                 10,
-                3
+                2
             );
             add_action(
                 'woocommerce_subscription_validate_payment_meta',
@@ -197,12 +197,12 @@ public function update_subscription_status_for_direct_debit($renewal_order)
 
     /**
      * @param          $renewal_total
-     * @param WC_Order $renewal_order
+     * @param WC_Order|false $renewal_order
      *
      * @return array
      * @throws InvalidApiKey
      */
-    public function scheduled_subscription_payment($renewal_total, WC_Order $renewal_order, $gateway)
+    public function scheduled_subscription_payment($renewal_total, $renewal_order, $gateway)
     {
         if (! $renewal_order) {
             $this->logger->debug($this->id . ': Could not load renewal order or process renewal payment.');
@@ -408,6 +408,8 @@ public function scheduled_subscription_payment($renewal_total, WC_Order $renewal
             // Log successful creation of payment
             $this->logger->debug($gateway->id . ': Renewal payment ' . $payment->id . ' (' . $payment->mode . ') created for order ' . $renewal_order_id . ' payment json response: ' . wp_json_encode($payment));
 
+            // phpstan:ignore [mollie-stub] Mollie Payment object exposes _links and mode as dynamic stdClass properties not covered by type definitions
+            // @phpstan-ignore-next-line
             if (isset($payment->_links->changePaymentState->href) && $payment->mode === 'test') {
                 $renewal_order->add_order_note('MOLLIE TEST MODE: URL to change payment state for renewal payment: <a href="' . $payment->_links->changePaymentState->href . '" target="_blank">' . $payment->_links->changePaymentState->href . '</a>');
             }
@@ -634,8 +636,8 @@ public function validate_subscription_payment_meta($payment_method_id, $payment_
      */
     public function update_failing_payment_method($subscription, $renewal_order)
     {
-        $subscription->update_meta_data('_mollie_customer_id', $renewal_order->mollie_customer_id);
-        $subscription->update_meta_data('_mollie_payment_id', $renewal_order->mollie_payment_id);
+        $subscription->update_meta_data('_mollie_customer_id', $renewal_order->get_meta('_mollie_customer_id', true));
+        $subscription->update_meta_data('_mollie_payment_id', $renewal_order->get_meta('_mollie_payment_id', true));
         $subscription->save();
     }