Bacs (formerly Bankers Automated Clearing House; BACS) is a UK payment method that allows merchants to accept payment by direct debit, with funds being taken directly from customer accounts. Bacs has been owned by Pay.UK since 2018, but the system was developed in the 1960s as a way for merchants to process transactions from their customers more efficiently. 

Bacs uses an automated system that allows banks to make transactions more quickly and securely than they could in person or by phone. Today, there are over 2 million merchants in the U.K., including major retailers like Tesco and Sainsbury's supermarkets, who use it to process payments.

Users need an account with one of the participating banks: Bank of England, Barclays, HSBC, Lloyds TSB, RBS/NatWest or Santander. The bank will set up an account with BACS Ltd., who will then record all transactions made through the system. 

All transactions are recorded in real time, so there's no delay between when customers make a payment and when it appears on their statement. If something happens and there's an error in recording a transaction – for example if it's declined due to insufficient funds – then it will be corrected automatically when the next payment goes through successfully.

For merchants, this helps prevent chargebacks, and increases profit.

Merchants can accept payments from customers who do not have an account with a member bank but who have signed up for an account at PayPoint Ltd., which handles all of these transactions on behalf of Bacs Payment itself. These merchants must register with PayPoint Ltd. before accepting any electronic payments; however, registration takes only minutes and doesn't require any additional paperwork or forms.