The short answer
Same-day ACH is a NACHA-operated service that allows ACH transactions (debits and credits) submitted by certain cutoff times to settle the same business day rather than the traditional next-business-day (T+1) or T+2. Launched in phases from 2016 to 2018 and expanded in 2021-2022 to raise the per-transaction cap to $1 million and add a fourth processing window. It's the ACH network's answer to real-time payments — cheaper than wires, slower than FedNow/RTP, broadly adopted.
The processing windows (2026)
- Window 1: Submission cutoff 10:30 AM ET → settlement 1:00 PM ET.
- Window 2: Submission cutoff 2:45 PM ET → settlement 5:00 PM ET.
- Window 3: Submission cutoff 4:45 PM ET → settlement 6:00 PM ET.
- Standard non-same-day ACH: files submitted throughout the day, settled T+1 or T+2 depending on SEC code.
What it costs
- NACHA network fee for same-day: ~$0.052 per entry (shared between originating and receiving banks).
- Merchant-facing fee: $0.15-$1.00 per entry at most ODFIs, depending on volume tier.
- Compare to standard ACH at $0.05-$0.25 per entry.
- Compare to a wire at $25-$50 per wire.
When operators use same-day ACH
- Emergency payroll: Employee missed a regular payroll run; send same-day ACH to settle today instead of tomorrow.
- Customer disbursements / refunds: Pay claimants, refund large customers, disburse marketplace payouts.
- B2B urgent invoice payments: Under $1M, beats a wire on cost, better than overnight.
- Tax payments: Estimated taxes hitting the deadline day.
What operators need to know
- Returns still take T+2. Same-day ACH only speeds the initial settlement. Return codes come back on the same T+1 to T+60 schedule regardless. A same-day disbursement can still be clawed back up to 60 days later on an R10.
- Cutoffs are ET-strict. 2:45 PM ET means 2:45:00, not 2:45:30. If you're on the west coast and want window 3, you're submitting by 4:45 PM ET = 1:45 PM PT.
- Not every RDFI supports all three windows. Smaller credit unions may only credit same-day ACH on windows 1 and 2. Your ODFI can file for same-day, but if the receiving bank doesn't process the window, funds wait for the next business day.
- Compare to FedNow and RTP for real-time needs. FedNow and RTP settle in seconds, 24/7, with no $1M cap in RTP (FedNow caps at $500k). For truly real-time, they're the better tool.
- NACHA violation consequences. Same-day ACH carries the same return-code thresholds (0.5% unauthorized). Faster settlement doesn't change compliance.
- Integration in operator workflow. Most modern ODFIs allow origination via API in real time; treasury teams can trigger same-day disbursements programmatically for refunds, payouts, or accruals.