Return del to vendor- How delivery type determination

Hi All,

When i am creating return delivery to vendor in MBRL transaction code with reference to Material document, the system is creating delivery with RLL document type, want to understand how the system is determining RLL document type for 122 movement type vendor return delivery.

Do we have any assignment for delivery doc.type determination like how we have PO returns delivery.

Thanks in advance!

Regards

Lakshmikanth