Final answer:
A lockbox service is a banking service where payments are mailed to a unique post office box, allowing for quicker processing of paper checks.
Step-by-step explanation:
The method described for collecting customer cash receipts by sending remittance advice and a check to a bank's postal address is known as a lockbox service. This is a service provided by banks where business customers have their payments mailed to a unique post office box instead of to their business location. The bank then collects and processes these checks on behalf of the business, allowing for quicker deposit and funds availability. Unlike an electronic funds transfer (EFT) or use of an automated clearing house (ACH) which are both electronic payment methods a lockbox service still relies on the physical handling of paper checks. Furthermore, Check 21 refers to legislation allowing banks to handle checks electronically; however, it does not refer to a collection service itself.