Of the eight pages Google currently ranks for "ACH vs RTP vs FedNow", five quote a FedNow limit that has been wrong since November 2025, two still say the RTP cap is $1m, and one claims FedNow only runs between 7am and 7pm. Not one of them names an ISO 20022 message, shows an API payload, or explains why a FedNow "return" is a favour rather than a right.
This guide is the version I wanted when I first had to pick a rail per payout for a US treasury product. It covers the four domestic rails an engineer actually touches: ACH, RTP, FedNow and Fedwire, with CHIPS in a footnote. For each one: what the limit is and when it last changed, when the money moves, what messages carry it, what happens when it goes wrong, which legal regime governs the loss, and how the main US payment APIs expose the choice. It is the US counterpart to my Faster Payments vs Bacs vs CHAPS guide, and the mapping between the two is at the end for UK readers.
What Is the Difference Between ACH, RTP, FedNow and Fedwire?
All four settle in US dollars across accounts at the Federal Reserve. Three are operated by the Fed (FedACH, FedNow, Fedwire), one by a bank-owned private company (RTP, The Clearing House), and ACH has a second private operator, EPN, also run by The Clearing House. Everything else differs.
| ACH | RTP | FedNow | Fedwire Funds | |
|---|---|---|---|---|
| Operator | FedACH and EPN under Nacha rules | The Clearing House | Federal Reserve | Federal Reserve |
| Speed | Next banking day, or same day in three windows | Seconds, 24/7/365 | Seconds, 24/7/365 | Minutes, 22 hours a day on business days |
| Per-payment cap | $1m same-day (to $10m on 17 Sep 2027); none for standard | $10m (since 9 Feb 2025) | $10m network max (Nov 2025); $100k default per bank | None |
| Settlement | Deferred net, four times a banking day | Real-time, prefunded joint account at the Fed | Real-time gross, Fed master accounts | Real-time gross, Fed master accounts |
| Message format | Nacha fixed-width records | ISO 20022 | ISO 20022 | ISO 20022 since 14 Jul 2025 |
| Pull payments | Yes (debits) | No, Request for Payment only | No, Request for Payment only | No, drawdown request only |
| Reversible | Yes, return codes | No | No | No |
| 2025 volume | 35.2bn payments, $93tn | 447m payments, $1.45tn | 8.4m payments, $853bn | 217m transfers, roughly $1.15 quadrillion |
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About the Author
I'm Tom Wang, an AI Developer & Fintech Developer — building AI agents, crypto payment infrastructure, and cross-border payout systems with Rust, Go, and TypeScript. Based in London, UK.
Currently open to new opportunities in fintech, crypto payments, and AI agent engineering.
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