Why ACH matters
ACH is the workhorse of US consumer and business payments. Payroll, recurring subscriptions, B2B invoices, and most government disbursements move on ACH because it is dramatically cheaper than wires or card rails — pennies per transaction, not dollars. For a fintech, ACH is usually the lowest-cost way to pull money from a customer's bank account or push funds out.
When to use it
Use ACH for any payment where (a) you control the timing, (b) settlement in one to three business days is acceptable, and (c) cost matters more than speed. Classic fits: payroll, rent collection, recurring SaaS billing, marketplace payouts to verified sellers, and treasury sweeps between corporate accounts.
Common pitfalls
- Returns and NSFs. ACH debits can be returned for up to 60 days under some Nacha codes (R10 unauthorized). Returns cost money and bruise your sponsor bank's risk profile.
- Same-day vs standard. Same-day ACH is faster but capped and slightly more expensive. Don't promise instant — that's RTP or FedNow.
- Authorization discipline. You must hold proof of authorization for every debit. Sloppy authorization records are the fastest way to get program-managed off your sponsor bank's platform.
- Float games are dead. Modern Nacha rules and sponsor-bank scrutiny make legacy float-arbitrage business models non-viable.
For most fintechs, ACH is the baseline rail you optimize around, not a feature you advertise.