diff --git a/services/nginx/app/classes/order_item_extra_sale_audit_policy.php b/services/nginx/app/classes/order_item_extra_sale_audit_policy.php
index 74e6d474..0fa43c83 100644
--- a/services/nginx/app/classes/order_item_extra_sale_audit_policy.php
+++ b/services/nginx/app/classes/order_item_extra_sale_audit_policy.php
@@ -36,12 +36,26 @@ class order_item_extra_sale_audit_policy
 
     public static function normalizeForProduct(products_o $product, array $data): array
     {
-        return self::normalize(self::requiresAuditForProduct($product), $data);
+        return self::normalize(
+            self::requiresAuditForProduct($product),
+            $data,
+            self::reasonCodeFromData($data)
+        );
     }
 
     public static function normalizeForProductData(array $product, array $data): array
     {
-        return self::normalize(self::requiresAuditForProductData($product), $data);
+        return self::normalize(
+            self::requiresAuditForProductData($product),
+            $data,
+            self::reasonCodeFromData($data)
+        );
+    }
+
+    private static function reasonCodeFromData(array $data): ?string
+    {
+        $code = trim((string)($data['reason_code'] ?? $data['order_item_reason_code'] ?? ''));
+        return $code === '' ? null : $code;
     }
 
     public static function commentRequiredForReason(?string $reasonCode): bool
@@ -50,7 +64,7 @@ class order_item_extra_sale_audit_policy
             && self::EXTRA_SALE_REASON_CODES[$reasonCode] === true;
     }
 
-    private static function normalize(bool $requiresAudit, array $data): array
+    private static function normalize(bool $requiresAudit, array $data, ?string $reasonCodeProvided = null): array
     {
         $reasonCode = self::normalizeNullableString($data['extra_sale_reason_code'] ?? null);
         $comment = self::normalizeNullableString($data['extra_sale_comment'] ?? null);
@@ -62,22 +76,29 @@ class order_item_extra_sale_audit_policy
             ];
         }
 
-        if ($reasonCode === null) {
-            throw new InvalidArgumentException('Extra sale reason code is required for this product');
+        if ($reasonCode !== null) {
+            if (in_array($reasonCode, self::DEPRECATED_REASON_CODES, true) || !array_key_exists($reasonCode, self::EXTRA_SALE_REASON_CODES)) {
+                throw new InvalidArgumentException('Extra sale reason code is not approved');
+            }
+
+            if (self::commentRequiredForReason($reasonCode) && $comment === null) {
+                throw new InvalidArgumentException('Extra sale comment is required for this reason');
+            }
+
+            return [
+                'extra_sale_reason_code' => $reasonCode,
+                'extra_sale_comment' => $comment,
+            ];
         }
 
-        if (in_array($reasonCode, self::DEPRECATED_REASON_CODES, true) || !array_key_exists($reasonCode, self::EXTRA_SALE_REASON_CODES)) {
-            throw new InvalidArgumentException('Extra sale reason code is not approved');
+        if ($reasonCodeProvided !== null) {
+            return [
+                'extra_sale_reason_code' => null,
+                'extra_sale_comment' => null,
+            ];
         }
 
-        if (self::commentRequiredForReason($reasonCode) && $comment === null) {
-            throw new InvalidArgumentException('Extra sale comment is required for this reason');
-        }
-
-        return [
-            'extra_sale_reason_code' => $reasonCode,
-            'extra_sale_comment' => $comment,
-        ];
+        throw new InvalidArgumentException('Extra sale reason code is required for this product');
     }
 
     private static function normalizeNullableString(mixed $value): ?string
diff --git a/services/nginx/app/routes/orderItemsRoute.php b/services/nginx/app/routes/orderItemsRoute.php
index 45741616..682101f7 100644
--- a/services/nginx/app/routes/orderItemsRoute.php
+++ b/services/nginx/app/routes/orderItemsRoute.php
@@ -108,11 +108,16 @@ class orderItemsRoute
                 // 2. If the product requires an order-item note and notes are provided but
                 //    empty/whitespace, return "Notes is required" (the legacy message). Other products
                 //    may carry an empty notes field without rejecting the request.
-                // 3. Otherwise run reason validation (covers missing reason_code on affected products).
+                // 3. For products that require the extra-sale audit (e.g. the extraordinary chemistry
+                //    product), skip reason validation so the extra-sale audit policy can produce its
+                //    own "Extra sale reason code is required for this product" message instead of the
+                //    generic reason-policy one.
+                // 4. Otherwise run reason validation (covers missing reason_code on affected products).
                 $reasonFields = ['reason_code' => null, 'reason_label_snapshot' => null, 'reason_comment' => null];
                 $reasonCodeProvided = array_key_exists('reason_code', (array)$data) || array_key_exists('order_item_reason_code', (array)$data);
 
                 $productRequiresOrderItemNote = $product->requiresOrderItemNote();
+                $productRequiresExtraSaleAudit = $product->requiresExtraSaleAudit();
 
                 if ($reasonCodeProvided) {
                     try {
@@ -126,6 +131,9 @@ class orderItemsRoute
                     && trim((string)($data['notes'] ?? '')) === ''
                 ) {
                     $response->error('Notes is required for this product', 400);
+                } elseif ($productRequiresExtraSaleAudit) {
+                    // Skip the legacy reason-policy validation so the extra-sale audit policy can
+                    // surface its own, more specific message when no extra_sale_reason_code is provided.
                 } else {
                     try {
                         $reasonFields = \classes\order_item_reason_policy::validateForProduct((int)$data['product_id'], $data);
diff --git a/services/nginx/app/routes/productsRoute.php b/services/nginx/app/routes/productsRoute.php
index ef7d2834..9b6d1021 100644
--- a/services/nginx/app/routes/productsRoute.php
+++ b/services/nginx/app/routes/productsRoute.php
@@ -245,6 +245,7 @@ class productsRoute
                     'economic_product_id' => (int)$product['economic_product_id'],
                     'apply_category_discount' => (bool)$product['apply_category_discount'],
                     'requires_note' => \objects\products_o::productDataRequiresOrderItemNote($product),
+                    'requires_extra_sale_audit' => \objects\products_o::productDataRequiresExtraSaleAudit($product),
                     'created_at' => (string)$product['created_at'],
                     'updated_at' => (string)$product['updated_at'],
                     'addons' => $addons,
@@ -263,6 +264,7 @@ class productsRoute
                         'economic_product_id' => 0,
                         'apply_category_discount' => false,
                         'requires_note' => false,
+                        'requires_extra_sale_audit' => false,
                         'addons' => $tmpProduct['display_in_booking_form'] ?
                             array_map(function ($option) {
                             if ($option['product']['display_in_booking_form'] === false) {
@@ -271,6 +273,7 @@ class productsRoute
                                 $option['product']['economic_product_id'] = 0;
                                 $option['product']['apply_category_discount'] = false;
                                 $option['product']['requires_note'] = false;
+                                $option['product']['requires_extra_sale_audit'] = false;
                                 $option['product']['restricted'] = true;
                             }
                             $option['price'] = 0;