Automated Clearing House
An automated clearing house is a network that moves money between bank accounts in batches — payroll, direct debits, bill payments, account-to-account transfers — by collecting instructions from originating banks, netting them and settling the results across central-bank accounts, once or a few times a day. The US ACH network is the largest; every country has an equivalent, and every fintech paying out or pulling funds by bank transfer rides one.
- Also known as
- ACH, ACH network, Bank-to-bank batch payments
- Used at
- payroll, benefits, bill payment, direct debits, account funding for fintechs, marketplace payouts, B2B payments — the US ACH moved about $86 trillion in 33 billion payments in 2024
- Binding
- the operator's rules (Nacha in the US; the equivalent scheme rules for Bacs in the UK, SEPA in the euro area); originators sign agreements with their banks and bear return and fraud liability
- Typical timing
- next-day settlement standard; same-day ACH in three daily windows since 2016, with a $1m per-payment limit; returns (insufficient funds, unauthorised) can arrive days later — two business days for most, 60 days for consumer unauthorised debits
- Typical cost
- cents per transaction, against 2–3% for cards — which is why fintechs push customers to fund accounts and pay by bank transfer
- Parties
- the originator (the fintech or its customer), the originating bank (ODFI), the operator, the receiving bank (RDFI), and the account holder on the other end
How an automated clearing house works in practice
A fintech pays 50,000 gig workers on Friday. It sends a file to its bank — 50,000 credit instructions with amounts and account numbers; the bank submits it to the ACH operator in the day's window; the operator sorts the entries by receiving bank, nets each bank's position, and settles the net amounts across the banks' Federal Reserve accounts; the receiving banks post the credits to the workers' accounts the next morning, or the same afternoon under same-day ACH. For a debit — a subscription pulling a monthly fee — the flow is reversed and the risk is different: the money arrives, and the payer's bank can return it days later if the account was empty or the payer disputes the authorisation.
The design is cheap and slow by choice: batches, netting and a few settlement windows a day make a transaction cost cents, at the price of hours to days of latency and the return risk that follows. Fintechs build around both — checking account balances through open banking before pulling a debit, holding funds until the return window passes, and using same-day windows where speed is worth the fee. The instant alternatives (RTP, FedNow in the US; Faster Payments in the UK; SEPA Instant in Europe) settle in seconds and irrevocably, and are taking the time-sensitive flows.
For a payments company the ACH connection is a bank relationship: origination limits, return-rate thresholds (Nacha caps unauthorised returns at 0.5%), and a bank that can withdraw the service.
Example
A neobank funds customer accounts by ACH debit from external bank accounts. It pulls $40m a month across 300,000 debits at $0.15 each — $45,000 of cost, against the $1.2m the same funding by card would cost. Its return rate is 1.8% overall: 1.5% insufficient funds, 0.3% unauthorised — within Nacha's thresholds (15% administrative, 3% overall, 0.5% unauthorised). It holds funded balances for three business days before allowing withdrawals, which covers most NSF returns, and uses an open-banking balance check before debits above $500, cutting NSF returns by a third. A fraud ring opening accounts and pulling from stolen bank details produces a spike of unauthorised returns to 0.7% in one month; the ODFI's warning letter arrives before the fintech's own dashboard flags it.
Common mistakes
- Treating an ACH credit as final on arrival when the debit that funded it can still return. - Releasing funds before the return window on debits from new accounts. - Return rates unmonitored until the originating bank's letter. - Using next-day ACH for payouts customers expect in minutes, then paying for cards to fix it. - Assuming the ACH model is universal; SEPA, Bacs and the instant schemes have their own rules and clocks.