diff --git a/projects/ngx-paypal-lib/src/lib/models/paypal-models.ts b/projects/ngx-paypal-lib/src/lib/models/paypal-models.ts
index 0881416..afd2eee 100644
--- a/projects/ngx-paypal-lib/src/lib/models/paypal-models.ts
+++ b/projects/ngx-paypal-lib/src/lib/models/paypal-models.ts
@@ -132,6 +132,7 @@ export interface IPayPalTransaction {
     description?: string;
     custom?: string;
     payment_options?: IPayPalTransactionPaymentOptions;
+    invoice_number?: string;
     soft_descriptor?: string;
     item_list?: IPayPalTransactionItemList;
 }