The Automated Clearing House (ACH) network is the long-established workhorse of US bank payments. It handles direct deposit, bill pay, recurring payments, and a huge share of business transfers. Unlike the instant rails (FedNow and RTP), ACH processes payments in batches rather than one at a time, which makes it slower but keeps it broadly available and low-cost. This page explains ACH credit transfers, same-day ACH, and where ACH fits alongside the instant rails.
ACH handles both push payments (credit transfers, covered here) and pull payments (debits, used for recurring billing). For the pull side, see ACH debit and recurring billing.

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What an ACH credit transfer is

In an ACH credit transfer, the sender pushes money from their account to a recipient’s account. The classic example is payroll: an employer sends wages into employees’ accounts. Because ACH is batch-based, transactions are gathered and processed in scheduled windows rather than instantly.
ACH does not settle each payment on its own the moment it happens. Instead, payments are grouped and processed in set windows during business days. This is the key structural difference from FedNow and RTP.
Standard ACH operates on banking days, not around the clock. Payments initiated on a weekend or holiday wait for the next processing window.
Unlike the instant rails, ACH payments can be reversed under certain conditions. That reversibility is a safety net that instant, irrevocable payments do not offer.

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Standard vs. same-day ACH

To speed things up for time-sensitive payments, the network offers same-day ACH, which settles eligible payments within the same business day rather than over one to three days.
Same-day ACH is faster than standard ACH, but it is still not instant. Payments settle in windows during the business day, not continuously 24/7 the way FedNow and RTP do.

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ACH vs. the instant rails

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Why ACH is still everywhere

Even as instant payments grow, ACH remains dominant because it is cheap, universally supported, and well-suited to predictable, high-volume payments like payroll and subscriptions. Its reversibility is also genuinely useful for correcting mistakes, something the instant rails deliberately do not allow.
Most US businesses use more than one rail. A common pattern is ACH for routine, scheduled, high-volume payments, and FedNow or RTP for the smaller number of payments where speed and certainty are worth more than reversibility.