Final answer:
The document that accompanies the customer's payment is the remittance advice, which helps a business keep track of payments and match them to the corresponding invoices.
Step-by-step explanation:
The document that accompanies the customer's payment is the remittance advice. A remittance advice is a document sent by a customer to a business to indicate the payment of an invoice. It typically includes the customer's name, invoice number, payment amount, and payment date. The remittance advice helps the business keep track of payments and match them to the corresponding invoices.