diff --git a/includes/api/class-wc-checkoutcom-api-request.php b/includes/api/class-wc-checkoutcom-api-request.php
index 3b43bd9c..f6be4145 100644
--- a/includes/api/class-wc-checkoutcom-api-request.php
+++ b/includes/api/class-wc-checkoutcom-api-request.php
@@ -224,6 +224,7 @@ private static function get_request_param( WC_Order $order, $arg, $subscription
 			$payment_option = 'PayPal';
 
 			$method = new RequestPayPalSource();
+			$method->invoice_number = $order->get_id();
 
 		} elseif ( in_array( $arg, $apms_selected, true ) ) {
 			// Alternative payment method selected.