Enhanced systems and methods for processing invoices, payments, and money transfers are described. One aspect of the invention is a computer-implemented method (and corresponding system and computer program product) for inviting an entity to open an account at a billing and payment system, the method comprising: issuing a check payable to the entity, wherein a checkbox for opening an account at the billing and payment system is printed on an endorsement section of the check along with a reference to additional information regarding additional information related to the account opening; receiving an image of the endorsement section of the check after the check is cleared; determining whether the checkbox is checked in the image; and responsive to a determination that the checkbox is checked, opening an account for the entity at the billing and payment system.