ACH

ACH is what most American money movement actually rides on. The Automated Clearing House network, governed by Nacha rules and operated by the Federal Reserve and The Clearing House, processed 35.2 billion payments worth $93 trillion in 2025. Payroll, mortgages, utility bills, government benefits, and a growing share of business-to-business invoices all travel as ACH entries.

The design is the opposite of a wire. Rather than settling each payment individually the moment it arrives, ACH collects payments into batch files, exchanges them between banks in scheduled processing windows, and settles net positions. It is a textbook example of deferred net settlement: enormous gross volumes, a fraction of the value actually moving between banks, and clearing that happens hours before the money does.

Cheap by design, slow by design

Batching is why an ACH payment costs cents where a wire transfer costs tens of dollars, and it is also why ACH is slow. A standard entry settles in one to two business days. Same Day ACH, introduced in 2016 and expanded since, compresses that to hours: 1.4 billion payments worth $3.9 trillion used it in 2025, growing 16.7% by volume year over year. But even Same Day ACH runs in fixed daily windows with cut-offs, not continuously. A payment that misses the last window waits for the next business day, which is why the cut-off time still governs an ACH treasury operation’s daily rhythm.

ACH also settles provisionally. Entries can be returned for insufficient funds, closed accounts, or disputes days after they appear to complete, so an ACH credit is not final the way an RTGS payment is. For payees, that return window is a real, if statistically small, source of uncertainty that faster rails have removed.

Reach

ACH is a purely domestic rail. Cross-border payments touch it only at the edges: an international payment that starts or ends in the US typically converts to or from an ACH or wire leg, with the cross-border segment handled by correspondent banking or an alternative network. The IAT (International ACH Transaction) format standardizes how those legs carry the required originator and beneficiary information, but the ACH network itself never leaves the United States.