Interchange-Plus vs. Flat-Rate Processing: How to Compare Quotes

Two processing quotes land in your inbox. One promises a simple flat rate. The other offers interchange-plus, with a smaller percentage followed by a few cents per transaction. Which one costs less? You cannot tell from those headline numbers alone. The useful comparison is what each offer would charge for the same month of business, including the fees that sit outside the advertised rate.

Here is how to put both quotes on the same footing without turning the exercise into an accounting project.

What interchange-plus actually means

Interchange-plus separates underlying card costs from the provider’s markup. Your quote might describe that markup as a percentage, a per-transaction amount, or both. Ask which network fees are passed through separately and whether any account charges are added each month.

The “plus” is only part of your bill. Your total can change with the cards customers use, how payments are accepted, and the applicable transaction categories. A small markup does not mean every sale carries the same total processing rate. Visa’s explanation of rates and fees distinguishes interchange between financial institutions from the merchant charges a business negotiates with its provider.

What a flat rate does—and does not—cover

Flat-rate pricing bundles processing costs into a stated charge for a particular payment method. That can make forecasting easier. But “flat” does not necessarily mean one price for every way a customer pays.

An in-person payment, an online order and a manually entered card may have different prices. Software, hardware and optional services may also be billed separately. For a real-world example of why payment method matters, Square’s published pricing separates payment types and plan options. Check your actual written offer rather than assuming an advertised rate covers everything.

Collect five numbers before comparing

Start with a complete, representative statement. If your business is seasonal, use several months so a quiet period does not set the wrong expectations. Our guide to reading a merchant processing statement explains where to find the figures.

• Total card sales for the period.
• Number of transactions and average ticket size.
• Share of payments taken in person, online and by manual entry.
• All recurring processing and account charges.
• Separate software, equipment and support costs.

Ask both providers to price that same activity. A quote based on counter payments is not a fair comparison with a statement that includes substantial telephone or online business. Also check how refunds and disputed transactions would be charged.

A worked comparison using hypothetical quotes

Suppose a business processes $30,000 across 600 transactions in one month. The following figures are invented solely to demonstrate the calculation. They are not Champion Payments rates, competitor quotes, or a forecast of your interchange costs.

For the interchange-plus example, assume the underlying card costs total $540. The hypothetical provider adds 0.30% of sales, 10 cents per transaction and a $20 monthly charge. That produces:

• Underlying card costs: $540.
• Percentage markup: $30,000 × 0.30% = $90.
• Transaction markup: 600 × $0.10 = $60.
• Monthly charge: $20.
• Total: $710, or approximately 2.37% of card sales.

For the flat-rate example, assume 2.60% plus 10 cents per transaction and no monthly processing charge. The calculation is $780 plus $60, for a total of $840, or 2.80%. Under these assumptions, the first quote costs $130 less.

Now change just one assumption: underlying card costs rise from $540 to $680 because the transaction mix changes. The interchange-plus total becomes $850. The flat-rate total remains $840 under the hypothetical offer. The result reverses. That is why the pricing model’s name cannot settle the decision for you.

Average ticket size changes the comparison

A per-transaction charge is easy to overlook when the percentage looks attractive. At 10 cents each, 600 transactions cost $60. At the same sales volume, 1,200 transactions cost $120. Smaller tickets mean more individual charges for each dollar collected.

Ask for another calculation if your transaction count is likely to change. A coffee counter and an auto repair shop can have identical monthly card sales and very different payment patterns. Your quote should reflect yours.

Check the costs of switching and staying

Before choosing a provider, read the contract alongside the cost comparison. Ask about cancellation terms, equipment ownership, leases, software subscriptions and any fees that apply when the account is quiet. Confirm whether the POS system lets you change processors without replacing the hardware or software.

Keep processing costs and operating costs visible as separate subtotals, then compare the combined expense. A lower processing bill is less useful if it requires a software subscription or equipment commitment you did not include. Ask which charges can change and how you will be notified.

Choose from a complete comparison

A useful quote explains the numbers, its assumptions and its limits. It should also make clear who helps when a payment fails or a deposit needs investigating. If the written offer leaves those questions unanswered, get the details before signing.

Our payment processing service explains Champion’s approach. If you would rather start with the statement you already have, request a free merchant statement audit. The goal is a clear comparison of your actual costs, not a decision based on the smallest number in an advertisement.