Merchant Account Pricing Models Explained: Tiered, Flat Rate, and Interchange-Plus

When you sign up for a merchant account, one of the most important decisions you will make is how you agree to be charged for processing. Most business owners spend more time picking their terminal than understanding their pricing model, and that is a mistake that can quietly cost real money over time.

There are three main pricing models used by processors today: tiered pricing, flat-rate pricing, and interchange-plus. Each works differently, and each has tradeoffs worth understanding before you sign anything.

How tiered pricing works

Tiered pricing was the industry standard for decades and is still widely used. Under this model, every transaction is sorted into pricing tiers — commonly three, but some processors use two, four, or more depending on how their plans are structured. The most common setup has a qualified tier, a mid-qualified tier, and a non-qualified tier. Qualified transactions get the best rate. Mid- and non-qualified transactions get hit with a surcharge on top of the base rate.

The problem is that the processor decides which transactions land in which tier, and the criteria are rarely explained clearly. Rewards cards, corporate cards, keyed-in transactions, and others routinely fall into the higher tiers. It is not unusual for 30% or more of a business’s transactions to downgrade, which can significantly inflate what looks like a competitive base rate.

When a processor quotes you “1.69% qualified,” that number only tells part of the story. The mid-qualified surcharge might add another 0.75%, and the non-qualified surcharge another 1.50% or more on top of that. Your actual effective rate can end up well above what you thought you were signing up for, and it is genuinely difficult to audit your statement to figure out where the money went.

How flat-rate pricing works

Flat-rate pricing is simple by design. You pay one rate on every transaction regardless of card type, how it was entered, or any other variable. Payment aggregators like Square and Stripe built their businesses on this model.

It is worth noting that Square actually charges different rates depending on how a card is accepted — in-person tap or chip transactions, keyed-in transactions, and online transactions each have their own rate. That is technically a form of tiered pricing. The reason it still feels like flat-rate is that merchants control how they accept cards. If you never key in a sale, you always pay the same in-person rate. The tiers exist, but a disciplined merchant can stay in the lowest one consistently.

Square currently charges 2.6% + $0.15 for in-person transactions. Stripe is at 2.9% + $0.30 for online payments. The simplicity is real, and for very small businesses or those just getting started, it has genuine value. You always know roughly what you will pay.

The tradeoff is that flat-rate pricing is a one-size-fits-all solution. The rate has to be set high enough to cover every card type, including the expensive rewards and corporate cards that cost more to process. Businesses with a good card mix — mostly basic consumer cards processed in person — end up subsidizing the cost of everyone else. As volume grows, that premium adds up. Most businesses processing more than $10,000 to $15,000 per month are likely overpaying compared to what a properly structured merchant account would cost them.

How interchange-plus pricing works

Interchange-plus pricing separates two things that other models bundle together: the wholesale cost of the transaction and the processor’s markup.

The wholesale cost is interchange. It is set by Visa, Mastercard, Discover, and American Express, and it is the same for every processor. Nobody negotiates it. A basic consumer card swiped in person sits in a different interchange category than a premium rewards card or a corporate card, and those differences show up clearly on your statement. These rates are published publicly and change twice a year, in April and October. In general, in-person consumer card transactions run lower than key-entered or online transactions, which carry more fraud risk and are priced accordingly by the card networks.

The plus in interchange-plus is your processor’s markup. This is the part that is actually negotiable, and it is the same on every transaction regardless of card type.

What this means in practice is full transparency. Your statement shows exactly what went to the card networks and exactly what went to your processor. You can verify both. You can compare processors on an equal footing because the markup is isolated and visible.

Which model is right for your business

Flat-rate pricing makes sense if you are very early stage, processing low volume, or value simplicity above all else. There is nothing wrong with starting there.

Tiered pricing is hard to recommend in most situations. The lack of transparency makes it difficult to know what you are actually paying or whether you are getting a fair deal. If you are on a tiered plan and want to understand your true effective rate, ask your processor to break down what percentage of your transactions are hitting each tier. If they cannot or will not tell you, that is worth paying attention to.

Interchange-plus is what we recommend for most businesses that are past the startup phase. Whether it is the cheapest option for any given merchant depends on the markup a processor offers, and that varies. What it does guarantee is that you can see exactly what you are paying and why. When rates change, you see it. When your card mix shifts, you understand how it affects your costs. That kind of visibility makes it easier to manage your processing over time and to have an informed conversation with your processor when something does not look right.

The bottom line

Pricing models are not just a technical detail buried in your merchant agreement. They determine how clearly you can see what you are paying and how much control you have over those costs. If your current processor cannot give you a plain explanation of how your transactions are being priced, that is worth addressing. We are happy to walk through your current statement and show you exactly where your processing dollars are going.

Note for review: approximately 920 words. Changes made: tiered section now notes variable number of tiers; flat-rate section explains Square’s structure and why it still functions like flat-rate for disciplined merchants; interchange-plus closing reframed around transparency and visibility rather than cost comparison; specific rate figures softened to general ranges to avoid accuracy risk.