The short answer
Flat-rate pricing is a payments model where the processor charges you one fixed rate (plus a per-transaction fee) for every card transaction, regardless of whether it was a debit card, a rewards credit card, a corporate card, or a foreign card. Stripe's "2.9% + $0.30 per transaction" is the archetypal example. Square, PayPal standard, and most other aggregators use variations of the same model.
How it compares to the alternatives
- Flat-rate: One rate for everything. You overpay on cheap cards and underpay on expensive ones; the processor keeps the spread.
- Tiered pricing: 3-6 tiers of rates, processor decides which tier each transaction lands in. See tiered pricing.
- Interchange-plus: Pass-through interchange cost plus a fixed markup. Transparent. See interchange-plus.
When flat-rate actually wins
- Under $20k/mo in volume. You're too small to negotiate interchange-plus and the simplicity is worth the premium.
- Heavy rewards credit-card mix. If 70% of your volume is premium rewards cards, flat-rate's blended price may beat pass-through interchange.
- You value predictable math more than savings. Flat-rate means your CFO can model cost as a single percentage instead of a moving target. For subscription businesses with tight unit economics, predictability has a value.
- You're seasonal and running under a minimum. Flat-rate aggregators don't charge monthly minimums. A dedicated merchant account on interchange-plus might charge you $25-$250 in months where you do zero volume.
When flat-rate stops being the right answer
- Above $30k/mo. The savings from interchange-plus at this volume typically run $300-$1,200/mo, which more than pays for the statement complexity. At $100k/mo the savings are usually $1,500-$5,000/mo.
- Debit-heavy or card-present portfolios. Flat-rate eats all the debit savings. Durbin-capped debit interchange is 0.05% + $0.21 — you're paying 2.9% on that and the processor is pocketing 2.85% clean.
- Multi-brand operators. Once you consolidate $200k+/mo across brands, every basis point matters. See the math in our multi-brand savings calculator.
What operators need to know
- "Flat-rate" is a marketing term, not a regulatory one. Two flat-rate processors can differ 50+ basis points apart. Compare the headline number before reading the contract.
- The per-transaction fee kills small tickets. $0.30 on a $15 order is 2% on top of the 2.9%. Your real effective rate on a portfolio with $20-$30 AOV is 4.0-4.5%.
- Flat-rate processors reserve the right to reprice you. Stripe has raised its flat rate twice in the last decade. Built-in pricing power flows to the processor.
- Flat-rate is not safe for high-risk. Stripe, Square, and PayPal don't underwrite high-risk verticals at flat-rate; they drop the account instead. If you're in peptides, CBD, or kratom, flat-rate isn't available as a stable option — see our high-risk payment gateway explainer.