Point of sale (POS) (also sometimes referred to as Point of purchase (POP) ) or checkout is the location where a transaction occurs. A "checkout" refers to a POS terminal or more generally to the hardware and software used for checkouts, the equivalent of an electronic cash register.

A POS terminal manages the selling process by a salesperson accessible interface. The same system allows the creation and printing of the receipt.

Early Electronic Cash Registers (ECR) were controlled with proprietary software and were very limited in function and communications capability. In August 1973 IBM announced the IBM 3650 and 3660 Store Systems that were, in essence, a mainframe computer used as a store controller that could control 128 IBM 3653/3663 point of sale registers. This system was the first commercial use of client-server technology, peer-to-peer communications, local area network (LAN) simultaneous backup, and remote initialization. By mid-1974, it was installed in Pathmark Stores in New Jersey and Dillard's Department Stores.