The API allows merchants to directly offer merchant-funded USPS return labels from their own websites. The Domestic Returns API offers labels of three different sizes (4x4, 4x6, 3x6) in either PDF or TIF formats for customer convenience. The return labels also each have an Intelligent Mail Package Barcode (IMpb) that can be tracked on USPS.com.

Important Note: In order to begin using the API, you must first become a registered user with the assistance of a USPS administrator (see contact information below).