diff --git a/src/Models/Invoice.php b/src/Models/Invoice.php
index 9d11e18..6aa84af 100644
--- a/src/Models/Invoice.php
+++ b/src/Models/Invoice.php
@@ -122,4 +122,8 @@ public function invoiceable()
     {
         return $this->morphTo('invoiceable');
     }
+    public function refundAmount()
+    {
+        return $this->payments()->where('method', 'REFUND')->sum('amount');
+    }
 }