Keep the official request, its verified instructions, the payer’s authorisation, transaction confirmation and any acknowledgement associating it with the application.
Make reconciliation possible
Record the participant and purpose alongside the transaction so processing fees and gifts cannot be confused. Keep sensitive account information in the agreed secure file. If an acknowledgement is missing or inconsistent, ask for clarification through the proper channel before concluding that payment completed the relevant stage.
Retain what makes reconciliation possible later, which is more than a bank confirmation. For each payment, keep the instruction that requested it with its date and reference, the details of the account to which it was sent, evidence of the verification you performed on those details, the debit record from the sending account, and the confirmation of receipt from the recipient. Record which stage and which person each payment relates to.
Where a payment covers more than one individual, note the breakdown. Keep the set together in date order rather than filed by document type, since the question that arises later is almost always about a particular payment and what it was for, and a chronological record answers it directly. Where a payment is made by a company rather than by the individual, keep the corporate authority for it alongside the payment record, since the question of who paid and on what authority tends to arise later and is far easier to answer from a contemporaneous document than from recollection.