Self-checkouts (SCOs), also known as assisted checkouts (ACOs) or self-service checkouts, are machines that provide a mechanism for customers to complete their own transaction from a retailer without needing a traditional staffed checkout. When using SCOs, customers scan item barcodes before paying for their total shop without needing one-to-one staff assistance. Self-checkouts are used mainly in supermarkets, although they are not uncommon in department or convenience stores. Most self-checkout areas are supervised by at least one staff member, often assisting customers process transactions, correcting prices, or otherwise providing service.

As of 2013, there were 191,000 self-checkout units deployed across the globe, and by 2025, it is predicted that 1.2 million units will be installed worldwide. The machines were originally invented by David R. Humble at Deerfield Beach, Florida-based company CheckRobot Inc., with NCR Corporation having the largest market share. They were introduced to the public in July 1986; the first machine, produced by CheckRobot, was installed in a Kroger store near Atlanta, Georgia.