Remittance advice tells a supplier which invoices you intended to pay. It does not, by itself, prove the payment was authorized under your internal rules or that the amounts matched approved invoices.
Keep the approved invoice (or invoice packet) with the same total, tax treatment, and purchase order reference. If your process uses goods receipts, the receipt should close the loop between ordered and received quantities before cash leaves the account.
Second, retain the approval record that matches your matrix—email trail, stamp, or system approval—tied to the amount paid. Approvals for a lower amount do not cover a higher remittance.
Third, keep the bank clearing evidence: statement line or confirmation that the exact amount left on the expected date. When these three sit with the remittance advice, payment audit work moves faster and disputes shrink.