A dated copy of the official program page and any implementing action, the intermediary's written material and contract, written identification of the payee and instrument, and a list of questions official sources do not answer.
Assemble the file before the transfer, not after
Hypothetical example: the couple pay first and start gathering documents when a problem appears. Reverse it. Save the official page as a dated PDF and repeat that each time it is consulted, along with any announcement that alters it.
Obtain the intermediary's brochure, emails and contract in full, including charges, promises and refund terms. Get written confirmation of who is to be paid, into which account, under what instrument, and what receipt will be issued. Write down every question that official material does not answer, so the gaps are visible rather than forgotten.
Keep this file where a family member or adviser could read it and understand the decision. Do not store banking credentials or passwords with it, and do not send identity documents to anyone whose role is unverified.