Which of the following must a remittance provider give to a sender when the sender pays for a remittance transfer?

The correct choice is that a remittance provider must give a receipt to the sender when they pay for a remittance transfer. A receipt serves as an important document that confirms the transaction took place, detailing the amount sent, the fees charged, and any other relevant transaction details. This is crucial for both record-keeping and accountability, ensuring that the sender has proof of the payment for any future references or disputes.

While a pre-payment disclosure informs the sender about the terms of the transfer, including fees and any relevant conditions before they make the payment, it is not mandatory for the provider to issue a separate pre-payment disclosure for every transaction, especially when focusing on what must be given at the time of payment. The other options, such as a discount or a safe harbor, do not represent standard requirements for remittance transactions. Thus, the issuance of a receipt stands out as the essential and formal requirement following a payment.