"Understanding U.S. ACH" (FK-ACH-003, Faisal Khan, July 2026) is a 27-page guide for compliance, operations, risk and product teams at money transfer companies, built on 21 cited Nacha, Federal Reserve and CFPB sources. It works from one distinction: an ACH credit (push) says "I am sending you money," an ACH debit (pull) says "I have permission to collect money from you" — and on a debit, the Receiver is the party being debited, not the party being paid.
The most expensive misunderstanding the guide corrects: settled funds are not immediately safe money. Two separate 60-day clocks run in parallel and are not the same clock — Nacha's unauthorized-debit return window runs from the original settlement date, while Regulation E's consumer error-resolution period runs from transmission of the statement on which the error first appears. Connecting a bank account through open banking is not the same as authorizing a debit either; Nacha has said authorization to share banking data is separate from authorization to initiate an ACH entry.
What the guide covers:
- The eight components an ACH pull actually requires, from a valid Regulation E authorization to fraud controls that run before origination, not after the return arrives
- Same Day ACH settlement windows and the per-payment limit rising from $1 million to $10 million on 17 September 2027
- The Nacha rule, effective 18 September 2026, requiring non-Same Day credits available by 9:00 a.m. local RDFI time on settlement date
- Why account takeover and social engineering are different fraud patterns with different Regulation E liability outcomes
- Nacha's debit-return benchmarks — 0.5% unauthorized, 3% administrative, 15% overall — treated as symptoms to monitor, not operational targets
- Three payout-timing models (immediate, risk-based, good funds) and the risk-based fraud-monitoring requirements taking effect 22 June 2026
The closing point: the real question is not whether ACH takes one or two days, but the gap between debit settlement and economic finality — that gap should drive funding and payout policy.