In the United States, the ACH Network is the national automated clearing house (ACH) for electronic funds transfers established in the 1960s and 1970s. It is a financial utility owned by US banks, and is one of the largest payments networks in the United States, both by volume and by customer reach; virtually every bank account in the US, whether personal or commercial, is connected to the network.

ACH has a wide variety of consumer and enterprise applications, processing financial transactions for consumers, businesses, and federal, state, and local governments. ACH processes large volumes of credit and debit transactions in batches. ACH credit transfers include direct deposit for payroll, Social Security, and other benefit payments, tax refunds, and vendor payments. ACH direct debit transfers include consumer payments on insurance premiums, mortgage loans, and other kinds of bills.

The rules and regulations that govern the ACH network are established and maintained by the nonprofit National Automated Clearinghouse Association (Nacha).

In 2018, the network processed 23 billion transactions with a total value of $51.2 trillion. Contrast this with the card payment networks in the US, which in the same time period processed under $10 trillion in payments.

The ideas leading to the ACH arose in the late 1960s, evolving from the existing US paper checks system. One early predecessor was a US federal initiative used to help United States Air Force personnel get their paychecks on time. The success of this initiative led to an expansion to other employees and the government adopted it as a major payroll standard.

Separately in 1968 a group of check clearinghouse associations set up The Special Committee on Paperless Entries (SCOPE) to build an automated payment system after concerns for the number of checks being cleared for payrolls. The participants were exchanging physical checks, and using magnetic ink character recognition (MICR) technology to extract the check information for the end recipient of the check, which led to the insight that a central system could use MICR to extract check data, and then exchange that information between participants, instead of the physical checks themselves.

This led to the first ACH association, formed in California in 1972. Other regional ACH associations followed. The difficulty in compliance between different organizations led them to unite to form National Automated Clearinghouse Association (Nacha) in 1974.

As with all social networks, ACH faced a chicken-or-the-egg problem in that it was difficult to convince consumers to want to move funds via this method if banks didn't support it, and it was difficult to convince banks to join the network if customers weren't clamoring to use ACH. Arguably the single most important event in the history of the development of ACH was the United States Social Security Administration trialing direct deposit of Supplemental Security Income via the ACH network in 1975. This meant that joining the network enabled banks' customers to receive Social Security benefits via direct deposit instead of via paper check, which drove many US banks to quickly sign up with the network.