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

Every time a customer swipes, dips, or taps a card, you pay to process that transaction. But how you pay depends entirely on your pricing model—and the model your processor put you on may be quietly eating into your margins. The two most common structures are flat-rate and interchange-plus. Understanding the difference is the first step to knowing whether you're overpaying.

How Flat-Rate Pricing Works

Flat-rate pricing is exactly what it sounds like: you pay one consistent rate for every transaction, regardless of card type. A typical example is 2.9% plus 30 cents per transaction. It's the model popularized by providers like Square, Stripe, and PayPal because it's simple and predictable.

The appeal is obvious. You always know what you'll pay, and there's no statement math to decode. For very small businesses or those processing low volume, that simplicity can be worth the premium.

But simplicity has a cost. Flat-rate processors bundle the actual network fees with their own markup into one number—and they keep the difference. When a customer pays with a low-cost debit card, you still pay the full flat rate, even though the underlying cost was a fraction of that.

How Interchange-Plus Works

Interchange-plus separates the two components you're actually paying for. "Interchange" is the non-negotiable fee set by Visa, Mastercard, and other networks. "Plus" is your processor's transparent markup, such as interchange plus 0.30% and 10 cents.

Because the markup is disclosed and the interchange passes straight through, you benefit directly whenever a transaction qualifies for a lower rate. Debit cards, rewards cards, and B2B transactions all carry different interchange costs, and interchange-plus lets you capture those savings instead of handing them to your processor.

Which One Is Costing You More?

For most established businesses processing meaningful volume—especially those handling a mix of card types or B2B payments—interchange-plus almost always wins. The transparency alone makes it easier to audit your statement and confirm you're not being overcharged.

Flat-rate pricing tends to make sense only at very low volumes, where the convenience outweighs the markup.

If you're processing more than a few thousand dollars a month and still on a flat rate, it's worth running the numbers. A quick statement review can reveal exactly how much that simplicity is costing you—and whether a switch would pay for itself almost immediately.