Term. Lockbox is a service provided by a bank to streamline the payment processes of an institution. Essentially, a lockbox is a post office box that the bank establishes and controls for an institution. The customers send their payments directly to this lockbox. The bank opens all correspondence, deposits the checks into designated accounts, and provides daily reports of deposit information. The institution receives a single daily electronic file of all remittance detail. The institution imports this file to update its accounts receivable system.