diff --git a/docsource/modules180-190.rst b/docsource/modules180-190.rst
index e7f797ce076..ef8a1450035 100644
--- a/docsource/modules180-190.rst
+++ b/docsource/modules180-190.rst
@@ -232,7 +232,7 @@ Module coverage 18.0 -> 19.0
 +---------------------------------------------------+----------------------+-------------------------------------------------+
 | http_routing                                      |Nothing to do         |                                                 |
 +---------------------------------------------------+----------------------+-------------------------------------------------+
-| iap                                               |                      |No DB layout changes.                            |
+| iap                                               |Done                  |Backfill service_id from legacy service_name.    |
 +---------------------------------------------------+----------------------+-------------------------------------------------+
 | iap_crm                                           |                      |No DB layout changes.                            |
 +---------------------------------------------------+----------------------+-------------------------------------------------+
diff --git a/openupgrade_scripts/scripts/iap/19.0.1.1/post-migration.py b/openupgrade_scripts/scripts/iap/19.0.1.1/post-migration.py
new file mode 100644
index 00000000000..4fda36de020
--- /dev/null
+++ b/openupgrade_scripts/scripts/iap/19.0.1.1/post-migration.py
@@ -0,0 +1,36 @@
+# Copyright 2026 Ledo
+# License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl).
+
+from openupgradelib import openupgrade
+
+
+@openupgrade.migrate()
+def migrate(env, version):
+    # The legacy column was named when an earlier major-version migration
+    # preserved iap_account.service_name; depending on the DB's history the
+    # prefix can be openupgrade_legacy_<N>_0_*. Look it up dynamically.
+    env.cr.execute(
+        """
+        SELECT column_name
+          FROM information_schema.columns
+         WHERE table_name = 'iap_account'
+           AND column_name LIKE 'openupgrade_legacy_%_service_name'
+         ORDER BY column_name
+         LIMIT 1
+        """
+    )
+    row = env.cr.fetchone()
+    if not row:
+        return
+    legacy_col = row[0]
+    openupgrade.logged_query(
+        env.cr,
+        """
+        UPDATE iap_account a
+        SET service_id = s.id
+        FROM iap_service s
+        WHERE a.service_id IS NULL
+          AND a.%s = s.technical_name
+        """
+        % legacy_col,
+    )