diff --git a/README.md b/README.md
index 9655e07..8e63579 100644
--- a/README.md
+++ b/README.md
@@ -282,7 +282,9 @@ Remember: All keys in "order array" must be in lowercase.
     $refund = OpenPayU_Refund::create(
         'Z963D5JQR2230925GUEST000P01', //as a value use ORDER_ID
         'Money refund', //Description - required
-        '100' //Amount - If not provided, returns whole transaction, optional
+        '100', //Amount - If not provided, returns whole transaction, optional
+        'ext-customer-id', // External submerchant ID, required only for marketplace
+        'ext-refund-id' // External refund ID, required only for marketplace
     );
 ```
 
diff --git a/lib/OpenPayU/v2/Refund.php b/lib/OpenPayU/v2/Refund.php
index eecbdea..550763d 100644
--- a/lib/OpenPayU/v2/Refund.php
+++ b/lib/OpenPayU/v2/Refund.php
@@ -15,11 +15,13 @@ class OpenPayU_Refund extends OpenPayU
      * Function make refund for order
      * @param $orderId
      * @param $description
-     * @param int $amount Amount of refund in pennies
+     * @param null|int $amount Amount of refund in pennies
+     * @param null|string $extCustomerId Marketplace external customer ID
+     * @param null|string $extRefundId Marketplace external refund ID
      * @return null|OpenPayU_Result
      * @throws OpenPayU_Exception
      */
-    public static function create($orderId, $description, $amount = null)
+    public static function create($orderId, $description, $amount = null, $extCustomerId = null, $extRefundId = null)
     {
         if (empty($orderId)) {
             throw new OpenPayU_Exception('Invalid orderId value for refund');
@@ -34,7 +36,15 @@ public static function create($orderId, $description, $amount = null)
         );
 
         if (!empty($amount)) {
-            $refund['refund']['amount'] = (int)$amount;
+            $refund['refund']['amount'] = (int) $amount;
+        }
+
+        if (!empty($extCustomerId)) {
+            $refund['refund']['extCustomerId'] = $extCustomerId;
+        }
+
+        if (!empty($extRefundId)) {
+            $refund['refund']['extRefundId'] = $extRefundId;
         }
 
         try {