ACH vs. Check vs. Wire: Cash Flow Implications

The three rails

ACH (Automated Clearing House) settles in 1-3 business days at near-zero cost (\$0.20-\$1.00 per transaction). Most US business-to-business payments now move via ACH. Same-day ACH (settled the same business day before cutoff) costs slightly more but is becoming standard.

Paper checks settle when deposited and cleared, usually 2-7 days. Cost is a few cents in printing plus mailing. The 'float' (time between issuing and clearing) used to be a treasury management tool but has shrunk with digital deposit.

Wires settle same-day, often within hours, and cost \$15-50 outbound and \$0-15 inbound. They're irrevocable. Used for time-sensitive or large payments (real-estate closings, large payroll, international).

Forecasting implications

When you forecast cash, the relevant date is the settlement date, not the issue date. A check 'paid' on Monday may not clear until Thursday or the following Monday. ACH initiated Friday after cutoff settles Tuesday. Wires hit instantly.

Conservative practice: assume outbound checks clear in 3 business days, ACH in 2, wires same-day. For inbound, assume customer ACH lands the day after their initiation; check-by-mail can take 5-10 days from postmark to deposit clearance.

Cost, speed, and risk of each rail

ACH is the workhorse of B2B payments: low cost (often free or sub-$1 per transaction), 1-3 business day settlement, and same-day options available at a small premium. ACH is the right default for recurring vendor payments, payroll, and any disbursement where 1-2 day settlement is acceptable. The main risk is reversal — ACH can be returned for up to 60 days for consumer transactions, 2 days for business — so don't release goods or refund cash on receipt of an unverified ACH credit.

Wires are real-time and final: once sent, they cannot be reversed except in cases of obvious bank error. That makes them right for closings, large vendor payments where confirmation matters, and any payment over the limit your treasury policy sets. Wires are also expensive — $25-50 outgoing, $15-30 incoming — so reserving them for situations that need finality is the right discipline.

Checks are slow, expensive, and fraud-prone, but still ubiquitous in construction, real estate, and insurance. Positive pay (where you upload a list of checks you've issued and the bank rejects anything that doesn't match) is a near-mandatory control for anyone still issuing checks at scale; check fraud remains the most common form of business payment fraud per the AFP Payments Fraud Survey, year after year.