Your AP Controls Were Built For Reversible Payments

A founder I work with runs a 24-person services firm. Her AP clerk paid a $48K vendor invoice last month and caught a typo in the account number ten minutes after release. The bank told her the funds had already settled at the receiving institution within seconds and there was no recall mechanism. The vendor's name on the file was off by one letter. The right vendor never saw the money. Recovery turned into a small claims matter against the accidental recipient.

She used FedNow. Her bank had turned it on in February as the default for any payment under $25K, and the AP portal lets a single clerk send one with no second approval.

What changed

By the end of 2025, about 1,500 US banks had joined the FedNow network. RTP coverage on the other rail sits at most of the larger banks where growing companies keep operating accounts. The transaction cap moved to $10 million in late 2025. A March 2026 survey of 271 finance executives put adoption intent at nearly 70% of mid-market businesses within two years.

For AP teams, the meaningful change is not speed. It's finality. RTP and FedNow settle with finality the moment funds hit the receiving account. There is no ACH-style three-day reversal window. No recall code your bank can send. The closest analog is a wire, which is why wire transfers have always required dual approval, callback verification on new banking details, and a senior signoff over some threshold.

Most growing-company AP processes don't apply those controls to instant payments. The portal didn't force it, and the rail looked like ACH.

Where your process probably breaks

Three things to check this week.

Which rails your bank turned on by default. Some treasury platforms began routing payments under a threshold to RTP automatically in 2025 to capture the cost savings. The clerk pressing pay doesn't always see the rail decision. Pull a settlement report and check the rail by transaction.

Who can send an instant payment without a second approval. If a single login can move money on a final-settlement rail, your control posture for that rail is weaker than your wire posture. Whatever dollar threshold for dual approval you set on wires in 2019 needs to apply to anything routed through FedNow or RTP.

How vendor banking changes flow into your system. Email-based banking changes were already the most common B2B fraud vector. On an ACH rail you had two days to catch a misdirected payment. On an instant rail you have none. Callback verification to a phone number you already had on file, not the one in the new email, is the entire control.

Reversibility was an implicit safety net under ACH. Instant rails removed it. AP approvals built around the safety net stopped working the day the bank flipped the switch.

What to write into policy

A short addition to your AP policy this quarter. Any payment routed through FedNow or RTP requires the same approvals as a wire of the same amount. Vendor banking changes require callback verification regardless of rail. New vendors over a defined threshold get their first payment on ACH, not an instant rail, until banking details have been confirmed twice.

The vendor my client paid last month did get the money eventually. From the wrong account, through a settlement claim, six weeks later. The faster rail cost her six weeks of vendor relationship and two thousand in legal fees.