diff --git a/app/assets/javascripts/application_legacy.js b/app/assets/javascripts/application_legacy.js
index 18590f2a9..84138cd9b 100644
--- a/app/assets/javascripts/application_legacy.js
+++ b/app/assets/javascripts/application_legacy.js
@@ -18,7 +18,6 @@
 //= require_self
 //= require big
 //= require units-converter
-//= require validation-utils
 //= require migrate-units-form
 //= require article-form
 //= require unit-conversion-field
diff --git a/app/assets/javascripts/group-order-form.js b/app/assets/javascripts/group-order-form.js
index 81edda4d8..bbb9f2f2a 100644
--- a/app/assets/javascripts/group-order-form.js
+++ b/app/assets/javascripts/group-order-form.js
@@ -11,47 +11,14 @@ class GroupOrderForm {
     this.groupBalance = config.groupBalance;
     this.minimumBalance = config.minimumBalance;
 
-    ValidationUtils.setupCustomValidation(this.form$);
-
     this.initializeIncreaseDecreaseButtons();
     this.submitButton$.removeAttr('disabled');
-    this.initializeFormValidation();
   }
 
   initializeIncreaseDecreaseButtons() {
     this.articleRows$.each((_, element) => this.initializeOrderArticleRow($(element)));
   }
 
-  initializeFormValidation() {
-    this.form$.on('submit', (e) => {
-      // Update all validation messages first
-      this.articleRows$.each((_, row) => {
-        const row$ = $(row);
-        this.updateValidationMessages(row$);
-      });
-
-      // Check if form is valid - browser will prevent submission if invalid
-      if (!this.form$[0].checkValidity()) {
-        e.preventDefault();
-
-        // Show error messages for all invalid inputs
-        this.form$.find(':invalid').each((_, invalidInput) => {
-          const input$ = $(invalidInput);
-          if (input$.hasClass('goa-quantity')) {
-            // Trigger validation to show error message
-            ValidationUtils.validateNumericInput(input$);
-          }
-        });
-
-        // Focus on first invalid input
-        const firstInvalid = this.form$.find(':invalid').first();
-        if (firstInvalid.length > 0) {
-          firstInvalid.focus();
-        }
-      }
-    });
-  }
-
   initializeOrderArticleRow(row$) {
     const quantity$ = row$.find('.goa-quantity');
     const tolerance$ = row$.find('.goa-tolerance');
@@ -67,20 +34,29 @@ class GroupOrderForm {
     row$.find('.btn-ordering.increase').click((event) => this.increaseOrDecrease($(event.target).parents('.btn-group').find('input.numeric'), true));
 
     quantityAndTolerance$.change(() => {
+      this.updateValidationErrors(quantity$);
       this.updateMissingUnits(row$, quantity$);
       this.updateBalance();
-      this.updateValidationMessages(row$);
     });
     quantityAndTolerance$.keyup(() => quantity$.trigger('change'));
+  }
 
-    // Handle validation events for quantity field only
-    quantity$.on('invalid', (e) => {
-      e.preventDefault();
-      e.stopPropagation();
-      this.updateValidationMessages(row$);
-    });
+  updateValidationErrors(valueField$) {
+    const errorContainer$ = valueField$
+      // TODO: This parent().parent() is quite arbitrary:
+      .parent().parent();
+    errorContainer$.find('.quantity-field-invalid').remove();
 
-    this.updateValidationMessages(row$);
+    if (valueField$.is(':invalid')) {
+      if (valueField$[0].validity.stepMismatch || valueField$[0].validity.rangeUnderflow) {
+        const errorSpan$ = $(`<div class="quantity-field-invalid">${I18n.t('errors.step_error', {min: 0, granularity: valueField$.attr('step')})}</div>`);
+        errorContainer$.append(errorSpan$);
+      }
+      if (valueField$[0].validity.rangeOverflow) {
+        const errorSpan$ = $(`<div class="quantity-field-invalid">${I18n.t('errors.maximum_quantity_error', {max: valueField$.attr('max')})}</div>`);
+        errorContainer$.append(errorSpan$);
+      }
+    }
   }
 
   updateBalance() {
@@ -102,8 +78,8 @@ class GroupOrderForm {
     // determine bgcolor and submit button state according to balance
     var bgcolor = '';
     if (balance < this.minimumBalance) {
-      bgcolor = '#FF0000';
-      this.submitButton$.attr('disabled', 'disabled')
+        bgcolor = '#FF0000';
+        this.submitButton$.attr('disabled', 'disabled')
     } else {
       this.submitButton$.removeAttr('disabled')
     }
@@ -269,30 +245,5 @@ class GroupOrderForm {
     var remainder = Big(quantity).mod(packSize).toNumber();
     return (remainder > 0 && (Big(remainder).add(tolerance).toNumber() >= packSize));
   }
-
-  updateValidationMessages(row$) {
-    const quantity$ = row$.find('.goa-quantity');
-
-    if (quantity$.length === 0) return;
-
-    const inputElement = quantity$[0];
-
-    // Clear any existing validation state
-    inputElement.setCustomValidity('');
-
-    // Use ValidationUtils for validation with error spans
-    ValidationUtils.validateNumericInput(quantity$);
-
-    // Special case: item not available (max = 0)
-    const rawValue = quantity$.val().trim();
-    const inputValue = parseFloat(rawValue);
-    const maxValue = parseFloat(quantity$.attr('max'));
-
-    if (maxValue === 0 && inputValue > 0) {
-      const message = I18n.t('errors.item_not_available');
-      inputElement.setCustomValidity(message);
-      ValidationUtils.showValidationMessage(quantity$, message);
-    }
-  }
 }
 
diff --git a/app/assets/javascripts/unit-conversion-field.js b/app/assets/javascripts/unit-conversion-field.js
index a5773f076..08226d7d5 100644
--- a/app/assets/javascripts/unit-conversion-field.js
+++ b/app/assets/javascripts/unit-conversion-field.js
@@ -185,22 +185,14 @@
       const unitLabel = this.unitSelectOptions.find(option => option.value === unit).label;
       this.conversionResult$.text('= ' + this.getConversionResult() + ' x ' + unitLabel);
       this.conversionResult$.parent().find('.numeric-step-error').remove();
+      if (this.quantityInput$.is(':invalid')) {
+        this.applyButton$.attr('disabled', 'disabled');
 
-      const errorSpan$ = $('<div class="numeric-step-error"></div>');
-      
-      // Use ValidationUtils for proper custom error messages
-      const isValid = ValidationUtils.validateNumericInput(this.quantityInput$, {
-        errorSpan$: errorSpan$
-      });
-      
-      if (isValid) {
-        this.applyButton$.removeAttr('disabled');
+        const errorSpan$ = $(`<div class="numeric-step-error">${I18n.t('errors.step_error', {min: 0, granularity: this.quantityInput$.attr('step')})}</div>`);
+        errorSpan$.show();
+        this.conversionResult$.after(errorSpan$);
       } else {
-        this.applyButton$.attr('disabled', 'disabled');
-        if (errorSpan$.text()) {
-          errorSpan$.show();
-          this.conversionResult$.after(errorSpan$);
-        }
+        this.applyButton$.removeAttr('disabled');
       }
     }
 
diff --git a/app/assets/javascripts/validation-utils.js b/app/assets/javascripts/validation-utils.js
deleted file mode 100644
index 59cadcd08..000000000
--- a/app/assets/javascripts/validation-utils.js
+++ /dev/null
@@ -1,155 +0,0 @@
-// Shared validation utilities for form inputs
-class ValidationUtils {
-    /**
-     * Sets up custom validation messages while keeping browser validation active
-     * @param {jQuery} form$ - The form element
-     */
-    static setupCustomValidation(form$) {
-        if (form$.length === 0) return;
-
-        // Keep HTML5 validation active but override messages
-        // Don't set novalidate - we want the browser to prevent submission
-
-        // Set up custom validation for quantity inputs only
-        form$.find('input[type="number"].goa-quantity').each((_, input) => {
-            const input$ = $(input);
-
-            // Set up event handlers for custom validation messages
-            input$.on('invalid.customValidation', (e) => {
-                e.preventDefault(); // Prevent browser validation popup
-
-                // Apply our custom validation and show message in popover
-                ValidationUtils.validateNumericInput(input$, {
-                    showInSpanOnly: true // Don't use setCustomValidity for display
-                });
-            });
-        });
-    }
-    /**
-     * Validates a numeric input and sets custom validation messages
-     * @param {jQuery} input$ - The input element to validate
-     * @param {Object} options - Validation options
-     * @returns {boolean} - Whether the input is valid
-     */
-    static validateNumericInput(input$, options = {}) {
-        if (input$.length === 0) return true;
-
-        const inputElement = input$[0];
-        const rawValue = input$.val().trim().replace(',', '.');
-        const inputValue = parseFloat(rawValue);
-
-        let customMessage = '';
-
-        // Only validate if we have a valid number
-        if (rawValue !== '' && !isNaN(inputValue)) {
-            // Quantity field validation only
-            customMessage = ValidationUtils.validateQuantityField(input$, inputValue);
-        }
-
-        // Show validation message in error span (avoid popover conflicts)
-        ValidationUtils.showValidationMessage(input$, customMessage);
-
-        // Update visual error span if it exists (keep for backward compatibility)
-        if (options.errorSpan$ && options.errorSpan$.length > 0) {
-            if (customMessage) {
-                options.errorSpan$.text(customMessage).show();
-            } else {
-                options.errorSpan$.hide();
-            }
-        }
-
-        // Set custom validation message for browser validation
-        // This will be used by the browser to prevent form submission
-        if (!options.showInSpanOnly) {
-            inputElement.setCustomValidity(customMessage);
-        }
-
-        // Return validation state
-        return customMessage === '';
-    }
-
-    /**
-     * Validates a quantity field
-     * @param {jQuery} input$ - The quantity input element
-     * @param {number} inputValue - The parsed input value
-     * @returns {string} - Error message or empty string if valid
-     */
-    static validateQuantityField(input$, inputValue) {
-        // Get validation constraints from HTML attributes
-        const maxValue = input$.attr('max') ? parseFloat(input$.attr('max')) : null;
-        const minValue = parseFloat(input$.attr('min')) || 0;
-        const stepValue = parseFloat(input$.attr('step')) || 1;
-
-        // Check maximum quantity first (highest priority)
-        if (maxValue !== null && inputValue > maxValue) {
-            return I18n.t('errors.maximum_quantity_error', { max: maxValue });
-        }
-        // Check minimum value
-        else if (inputValue < minValue) {
-            return I18n.t('errors.step_error', { min: minValue, granularity: stepValue });
-        }
-        // Check step/granularity (allow for floating point precision issues)
-        else if (stepValue > 0) {
-            const remainder = ((inputValue - minValue) % stepValue);
-            if (Math.abs(remainder) > 0.0001 && Math.abs(remainder - stepValue) > 0.0001) {
-                return I18n.t('errors.step_error', { min: minValue, granularity: stepValue });
-            }
-        }
-
-        return '';
-    }
-
-    /**
-     * Shows or hides validation message using error spans (avoids popover conflicts)
-     * @param {jQuery} input$ - The input element
-     * @param {string} message - The validation message (empty to hide)
-     */
-    static showValidationMessage(input$, message) {
-        if (input$.length === 0) return;
-
-        // Find the error span for this input
-        const errorSpan$ = input$.closest('.group-order-input').find('.numeric-step-error');
-
-        if (message) {
-            // Show error message in span and add error styling
-            if (errorSpan$.length > 0) {
-                errorSpan$.text(message).show();
-            }
-            input$.addClass('validation-error');
-        } else {
-            // Hide error message and remove styling
-            if (errorSpan$.length > 0) {
-                errorSpan$.hide();
-            }
-            input$.removeClass('validation-error');
-        }
-    }
-
-    /**
-     * Hides all validation messages
-     */
-    static hideAllValidationMessages() {
-        $('.validation-error').removeClass('validation-error');
-        $('.numeric-step-error').hide();
-    }
-
-
-
-    /**
-     * Sets up validation for a form input
-     * @param {jQuery} input$ - The input element
-     * @param {Object} options - Validation options
-     */
-    static setupInputValidation(input$, options = {}) {
-        if (input$.length === 0) return;
-
-        // Only set up event handlers, don't trigger validation immediately
-        // to avoid recursion when called from existing event handlers
-        input$.on('invalid.validationUtils', (e) => {
-            e.preventDefault();
-            e.stopPropagation();
-            ValidationUtils.validateNumericInput(input$, options);
-            return false;
-        });
-    }
-}
\ No newline at end of file
diff --git a/app/assets/stylesheets/application.scss b/app/assets/stylesheets/application.scss
index 5b7785d3d..dbd57ebbf 100644
--- a/app/assets/stylesheets/application.scss
+++ b/app/assets/stylesheets/application.scss
@@ -11,4 +11,3 @@
 @import "list.missing";
 @import "recurring_select";
 @import "actiontext";
-@import "validation";
diff --git a/app/assets/stylesheets/bootstrap_and_overrides.css.scss b/app/assets/stylesheets/bootstrap_and_overrides.css.scss
index cee179f3e..299f2076b 100644
--- a/app/assets/stylesheets/bootstrap_and_overrides.css.scss
+++ b/app/assets/stylesheets/bootstrap_and_overrides.css.scss
@@ -314,7 +314,7 @@ tr.order-article {
 }
 
 .units_received_cell {
-  
+
 
   .btn-group .btn-ordering {
     margin-top: 0;
@@ -704,8 +704,7 @@ td.mr-1 > *:last-child {
   user-select: none;
 }
 
-.numeric-step-error {
-  display: none;
+.quantity-field-invalid {
   color: #b94a48;
 }
 
@@ -713,11 +712,6 @@ td.mr-1 > *:last-child {
   border: 1px solid #b94a48;
 }
 
-.btn-group.numeric-step:has(> input:invalid) + .numeric-step-error {
-  display: block;
-}
-
-
 .form-group .select2-container {
   width: 200px;
 }
diff --git a/app/assets/stylesheets/validation.scss b/app/assets/stylesheets/validation.scss
deleted file mode 100644
index b44d35826..000000000
--- a/app/assets/stylesheets/validation.scss
+++ /dev/null
@@ -1,19 +0,0 @@
-// Simple validation error styling for inputs
-input.validation-error {
-  border-color: #d9534f !important;
-  box-shadow: inset 0 1px 1px rgba(0,0,0,.075), 0 0 6px #ce8483 !important;
-  
-  &:focus {
-    border-color: #d9534f !important;
-    box-shadow: inset 0 1px 1px rgba(0,0,0,.075), 0 0 6px #ce8483 !important;
-  }
-}
-
-// Style error message spans
-.numeric-step-error {
-  color: #d9534f;
-  font-size: 12px;
-  font-weight: 500;
-  margin-top: 2px;
-  display: block;
-}
\ No newline at end of file
diff --git a/app/views/group_orders/_form.html.haml b/app/views/group_orders/_form.html.haml
index 698f19d6d..f1fd4c43d 100644
--- a/app/views/group_orders/_form.html.haml
+++ b/app/views/group_orders/_form.html.haml
@@ -116,7 +116,6 @@
             - quantity_data['used_quantity'] = @ordering_data[:order_articles][order_article.id][:used_quantity]
             - quantity_data['price'] = @ordering_data[:order_articles][order_article.id][:price]
             - quantity_data['minimum_order_quantity'] = @ordering_data[:order_articles][order_article.id][:minimum_order_quantity] unless @ordering_data[:order_articles][order_article.id][:minimum_order_quantity].nil?
-            - quantity_data['maximum_order_quantity'] = @ordering_data[:order_articles][order_article.id][:maximum_order_quantity] unless @ordering_data[:order_articles][order_article.id][:maximum_order_quantity].nil?
             - quantity_data['e2e-order-article-id'] = order_article.id
             %td.used-unused
               %span.used= number_with_precision(@ordering_data[:order_articles][order_article.id][:used_quantity], precision: 3, strip_insignificant_zeros: true)
@@ -129,8 +128,6 @@
                 %a.btn.btn-ordering.increase
                   %i.glyphicon.glyphicon-plus
                 %input.goa-quantity{type: "number", name: "group_order[group_order_articles_attributes][#{order_article.id}][quantity]", value: @ordering_data[:order_articles][order_article.id][:quantity], data: quantity_data, autocomplete: 'off', class: 'form-control numeric', style: ('display:none' if @order.stockit?), min: 0, max: (@ordering_data[:order_articles][order_article.id][:quantity_available]), step: order_article.article_version.group_order_granularity}
-              %span.numeric-step-error{style: 'display: none;'}
-                = t('errors.step_error', granularity: order_article.article_version.group_order_granularity, min: 0)
 
             %td.used-unused-tolerance{style: ('display:none' if @order.stockit?)}
               - if (order_article.article_version.uses_tolerance?)