Sponsorship agreement.
(6) Sponsorship agreement. A sponsoring entity must have a written sponsorship agreement (which may be part of another agreement between the sponsoring entity and the sponsored FFI) that refers to the requirements of a sponsored FFI under FATCA and that must be in place with each sponsored FFI for which the sponsoring entity acts by the later of March 31, 2019, or the date that the sponsoring entity begins acting as a sponsoring entity for the applicable sponsored FFI.