ACH vs wire vs RTP
Four US payment rails, four different answers to "when does the money arrive". The largest difference is not speed. It is which of them run on a Saturday.
The timing, side by side
| Rail | Settles in | Days it runs |
|---|---|---|
| ACH, standard | 1 to 2 banking days | Banking days only |
| ACH, Same Day | Hours, in three windows | Banking days only |
| Fedwire | Minutes, same day | Banking days only |
| RTP | Seconds | Every day, all year |
| FedNow | Seconds | Every day, all year |
ACH is a batch system
ACH does not move a payment when you submit it. Entries are collected into files and released in scheduled processing windows, which is why standard ACH settles one to two banking days later and why it costs cents rather than dollars. Same Day ACH shortens the wait to hours but does not change the model: it is still three batches a day. See how long an ACH transfer takes for the standard timing, and the Same Day cutoff windows for the deadlines.
ACH is also the only rail here with a defined return process. An entry can be returned under Nacha rules, which is the reason payroll and vendor payments still run on it rather than on something faster and final.
A wire is same day, and it is final
Fedwire settles each transfer individually and in real time, so funds are available the same day rather than one or two days later. Settlement is final and irrevocable: there is no return window, and recovering a misdirected wire depends on the receiving bank's cooperation rather than on a rule. That finality, plus a per-transfer fee measured in tens of dollars at retail, is what keeps wires on closings and large one-off transfers instead of on recurring payments.
Fedwire runs Monday through Friday and closes for federal holidays, the same calendar ACH uses. It also closes daily: the service shuts at 7:00 PM ET, and the deadline for customer transfers is 6:00 PM ET, earlier than that at most banks. A wire requested on a Saturday is a Monday wire.
RTP and FedNow do not stop
RTP, run by The Clearing House since 2017, and FedNow, run by the Federal Reserve since 2023, both settle in seconds and both operate 24 hours a day, every day of the year. Weekends and federal holidays make no difference to either. Both are credit push only, meaning the payer sends and nobody can pull, and both are final on settlement.
The catch is reach rather than timing. ACH gets to essentially every deposit account in the country. An instant payment only works if the receiving institution has joined that specific network, so the practical question is not whether the rail is open but whether the other side is on it.
Why the calendar is the real difference
Speed comparisons usually stop at seconds versus days, which understates the gap. A standard ACH file submitted on the Friday before a Monday federal holiday does not settle on Monday, and it may not settle on Tuesday either. The delay is not two days of processing. It is two banking days stretched across a four-day gap in the calendar.
That is the part worth checking before you promise anyone a date. Look up whether the Fed is open today, read the closure schedule for the year, or put a submission date into the settlement date calculator and get the answer for that file. Working backwards from a payday instead? Use the payroll cutoff calculator.
Building this into software rather than looking it up? The JSON API returns banking days, settlement dates, and the holiday schedule directly.