Flat Rate vs. Interchange-Plus: Which Pricing Model Is Costing You More?

Flat-rate pricing feels simple, but that simplicity has a cost. For most businesses processing over

0,000/month, interchange-plus is significantly cheaper — and the math isn't close.

When you signed up with your payment processor, you probably chose the simplest option: a flat rate. It's easy to understand — 2.6% + $0.10 on every transaction, no matter what. But that simplicity has a cost. For most businesses processing over

0,000 per month, interchange-plus pricing is significantly cheaper.

How Flat-Rate Pricing Works

Flat-rate processors like Square, Stripe, and PayPal charge a single percentage on every transaction regardless of card type. You pay the same rate whether a customer uses a basic debit card (low interchange) or an airline rewards credit card (high interchange). The processor pockets the difference between your flat rate and the actual card cost.

This model is profitable for processors because rewards and corporate cards — which make up a growing percentage of card transactions — carry interchange rates of 2.0–2.65%. On a 2.9% flat rate, the processor keeps 0.25–0.9% of every premium card swipe.

How Interchange-Plus Pricing Works

Interchange-plus (IC+) passes through the actual interchange rate for each transaction, then adds a fixed processor markup on top. Your statement shows the real cost of every card type, plus a transparent markup like 0.25% + $0.10.

When a customer pays with a basic debit card (interchange: 0.05% + $0.22), you pay that rate plus your markup. When they pay with a rewards card (interchange: 2.10%), you pay that rate plus your markup. Your processor makes the same margin on every transaction regardless of card type.

The Math: Which Is Actually Cheaper?

Let's compare at

0,000/month in volume with an average card mix: 30% debit, 40% basic credit, 20% rewards credit, 10% corporate. Blended interchange rate: approximately 1.59%.

  • Flat rate at 2.6%: $520/month in processing fees
  • IC+ at interchange + 0.20% + $0.10: approximately $370/month (assuming 300 transactions)
  • Monthly savings:
    50. Annual savings:
    ,800.

The savings grow larger as your volume increases and as your card mix shifts toward more rewards and corporate cards — which is the direction consumer spending is heading.

When Flat-Rate Is Actually Better

Flat-rate pricing isn't always wrong. It's the better choice for:

  • Very low volume: Under $5,000/month, the savings from IC+ are often wiped out by monthly fees.
  • Mostly debit transactions: If 80%+ of your transactions are debit cards, flat-rate is closer to your actual interchange cost.
  • Very small average ticket: On sub-
    0 transactions, the per-item fee on IC+ can make flat-rate more competitive.

Tiered Pricing: Avoid It

A third model worth mentioning: tiered pricing. Transactions are sorted into "qualified," "mid-qualified," and "non-qualified" buckets, each with a different rate. The processor controls which tier your transactions land in — and non-qualified rates can reach 4–5%. This model is used by legacy processors specifically because its complexity hides the true markup. Avoid it.

How to Switch to Interchange-Plus

If you're on flat-rate and processing over

0,000/month:

  1. Gather your last 2–3 monthly statements
  2. Calculate your current effective rate
  3. Get an IC+ quote from Helcim, Stax, or Dharma using your actual volume
  4. Compare total monthly cost including any fees
  5. If the savings justify it, switch — most IC+ processors are month-to-month

Use our free savings estimator to run the numbers using real Visa and Mastercard interchange tables.