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ACH (US) is slow, cheap, and reversible. Wire transfers are fast, expensive, and final. SEPA (EU) is between. Choosing between them is one of the most important architecture decisions for any money-moving product — and most consumer fintechs underestimate ACH's reversal risk (up to 60 days for unauthorized charges).
Compare the three major bank-transfer rails.
ACH (US) Wire (US) SEPA (EU) UPI (India) FedNow (US)
-----------------|-------------|-------------|-------------|--------------|-------------
Settlement T+1 to T+3 Same day T+1 to T+2 ~seconds ~seconds
Cost (sender) $0-0.25 $25-50 €0-0.50 ₹0 (banks) $0.045
Reversibility Up to 60d Effectively 0 ~5 business d Very limited Very limited
Limits $1M+/batch $999M+ €100k+ ₹100k+ $500k
Authorization NACHA Rules MT103/iso20022 SDD Mandate AEPS/PSP API ISO 20022
Use cases Payroll, B2B Large B2B Pan-EU P2P + retail Real-time B2B
subscriptions one-off SEPA Inst:rt instant
Returns (ACH):
R01-R85 codes
Most common:
R01 Insufficient funds (2 business days to know)
R03 No account / bad account (5 business days)
R10 Unauthorized (UP TO 60 DAYS)
Treating ACH as "settled" before R10 window closes is a leading cause of fintech losses.
Reversibility patterns:
ACH: "soft money" — never treat as final until 60 days
Wire: "hard money" — final on receipt
Cards: "softer" — chargebacks possible for 120-180 days
Why this matters for product design:
Subscription billing on ACH: hold service activation until R10 risk window passes
Marketplace payouts: don't pay sellers until buyer ACH funding clears
Trading platform: hold withdrawals 5 business days minimum for ACH-funded accounts