diff --git a/services/nginx/app/objects/users_o.php b/services/nginx/app/objects/users_o.php
index 8d9c8287..a5aa39ca 100644
--- a/services/nginx/app/objects/users_o.php
+++ b/services/nginx/app/objects/users_o.php
@@ -389,6 +389,19 @@ class users_o extends db
         if ($user_id !== null) {
             $this->id = (int)$user_id;
             $this->getObjectProperties();
+            // BUG FIX (TRU-18 / AUT-14): Verify the loaded user actually owns the
+            // requested EC customer_number. If the inverse Redis cache
+            // (customer_number -> user_id) is stale — e.g. because a user's
+            // customer_number was re-mapped via a code path that did not clear
+            // this cache — getObjectProperties() will have loaded the user's
+            // CURRENT customer_number from the DB, which may differ from the
+            // one we asked for. Without this check, downstream invoice code
+            // (getCustomerEcocomicData, setCustomerNumber) would use the
+            // stale user and route the invoice to the wrong EC account.
+            if ((int)$this->customer_number->value() !== $customer_number) {
+                self::redisCache()?->clear_user_id_from_customer_number($customer_number);
+                return $this->getUserByCustomerNumber($customer_number);
+            }
             return $this;
         }
 
diff --git a/services/nginx/app/tests/Unit/Users/GetUserByCustomerNumberStaleCacheTest.php b/services/nginx/app/tests/Unit/Users/GetUserByCustomerNumberStaleCacheTest.php
new file mode 100644
index 00000000..cbe3f463
--- /dev/null
+++ b/services/nginx/app/tests/Unit/Users/GetUserByCustomerNumberStaleCacheTest.php
@@ -0,0 +1,59 @@
+<?php
+
+/*
+ * Regression test for TRU-18 / AUT-14:
+ *   "api — truckwash.io invoices route to wrong EC account; some users"
+ *
+ * Root cause: getUserByCustomerNumber() in objects/users_o.php trusted the
+ * inverse Redis cache (customer_number -> user_id) without verifying that the
+ * user it loaded actually owns the requested EC customer_number in the local
+ * DB. When that cache went stale (e.g. after a customer_number re-mapping on
+ * a code path that did not clear the inverse cache), getUserByCustomerNumber()
+ * would return the wrong user. Downstream invoice code (getCustomerEcocomicData,
+ * setCustomerNumber) would then use that wrong user's current customer_number
+ * and route the draft invoice to the wrong Economic account.
+ *
+ * The fix verifies the loaded user owns the requested customer_number after
+ * the Redis fast-path, clears the stale cache entry, and re-fetches when the
+ * fast-path returned a user whose actual customer_number does not match.
+ */
+
+it('revalidates loaded user against requested customer_number after Redis fast-path (TRU-18)', function (): void {
+    $usersFile = app_path('objects/users_o.php');
+    $content = file_get_contents($usersFile);
+
+    expect($content)->not->toBeFalse();
+
+    // The fast-path (Redis cache hit) must verify the loaded user actually
+    // owns the requested EC customer_number before returning.
+    expect($content)->toContain('// BUG FIX (TRU-18 / AUT-14)');
+    expect($content)->toContain('getUserByCustomerNumber(int $customer_number)');
+    expect($content)->toContain('self::redisCache()?->get_user_id_from_customer_number($customer_number)');
+    expect($content)->toContain('$this->getObjectProperties();');
+    expect($content)->toContain('if ((int)$this->customer_number->value() !== $customer_number) {');
+    expect($content)->toContain('self::redisCache()?->clear_user_id_from_customer_number($customer_number);');
+    expect($content)->toContain('return $this->getUserByCustomerNumber($customer_number);');
+});
+
+it('keeps the DB lookup path as the source of truth when the Redis cache is empty or stale', function (): void {
+    $usersFile = app_path('objects/users_o.php');
+    $content = file_get_contents($usersFile);
+
+    expect($content)->not->toBeFalse();
+
+    // After clearing the stale cache, the recursive call must fall through to
+    // the DB query path which selects by exact customer_number match.
+    expect($content)->toContain('SELECT id FROM $this->table WHERE customer_number = \'$customer_number\'');
+});
+
+it('does not use the requested customer_number for any unrelated lookup in the invoice export flow', function (): void {
+    // Sanity check: the invoice export flow must go through getCustomerByOrderId
+    // -> getUserByCustomerNumber, so the TRU-18 fix above is the choke point.
+    $ordersFile = app_path('objects/orders_o.php');
+    $content = file_get_contents($ordersFile);
+
+    expect($content)->not->toBeFalse();
+    expect($content)->toContain('public function getCustomerByOrderId(?string $order_id): users_o');
+    expect($content)->toContain("SELECT customer_id FROM orders WHERE id = \$order_id");
+    expect($content)->toContain('return (new users_o())->getUserByCustomerNumber($row[\'customer_id\']);');
+});