The short version
- Flat rate favors simplicity but can charge the same markup across transactions with very different underlying costs.
- Interchange plus separates network and issuing-bank costs from the processor markup, which makes comparison easier when statements are complete.
- Dual pricing can reduce the shop's merchant credit-card percentage, but adds price-display, customer, and workflow responsibilities.
Flat rate vs interchange plus vs dual pricing is not a contest with one permanent winner. A 2.9% flat rate, interchange plus 30 basis points, and a 0% merchant credit-card rate are different machines. They move different costs and chores to the shop.
Start with three months of the same transactions. Run that identical pile through every proposal. If a salesperson changes the volume, card mix, or fees from one column to the next, bring the comparison back to level ground.
How the three models work
| Model | Basic structure | Owner tradeoff |
|---|---|---|
| Flat rate | One advertised percentage and often a transaction charge | Simple forecast, less visibility into underlying card cost |
| Interchange plus | Card-network and issuer cost plus a stated processor markup | More transparent, but monthly cost still changes with card mix |
| Dual pricing | Regular card price and lower cash price, with configured eligible credit transactions | Potentially lower merchant credit-card percentage, with added disclosure and customer workflow |
Flat rate: simple does not always mean inexpensive
Flat rate is easy to explain and easy to forecast. Swipe a card, pay the posted percentage and transaction charge. For a small mobile mechanic or a low-volume side of the business, that simplicity may be worth more than squeezing every basis point.
The tradeoff is that very different cards get pressed into the same price. Regulated debit may cost the provider much less than a premium rewards card, while the shop pays one flat percentage. Keyed, international, chargeback, hardware, and software charges can still live outside it.
Interchange plus: separate the cost from the markup
Interchange plus separates the underlying card cost from the processor's markup. That is useful when the statement actually shows the pieces. Owners can see what came from the card mix and what the provider chose to add.
The word plus is where the money hides. Ask for the percentage markup and cents per transaction, then list every monthly and event fee. 'Cost plus' without a written plus is not a proposal.
- Ask for the percentage and transaction markup.
- Confirm whether network assessments pass through at cost.
- List monthly minimums, PCI, gateway, batch, equipment, and annual charges.
- Model the offer with the shop's real card categories and transaction channels.
Dual pricing: a cost decision and a customer decision
A properly configured dual-pricing program can move eligible credit-card transactions to a 0% merchant processing rate while the regular card price reflects payment cost. It does not wipe the account clean. Monthly, debit, chargeback, gateway, and other fees can remain.
The other half of the bargain happens at the counter. The shop takes responsibility for clear prices, advisor training, debit tests, payment links, matching repair orders, and customer reaction. If nobody owns that work, the attractive rate can create an ugly pickup experience.
A clean proposal comparison
- Export or enter three months of transactions by card type and payment channel.
- Apply every proposal's percentage, per-transaction, monthly, equipment, gateway, and event fees.
- Model realistic changes in cash, debit, credit, ACH, check, and financing use.
- Add integration, reconciliation, staff-training, and contract costs.
- Compare funding, support, chargeback tools, refunds, equipment ownership, and cancellation terms.
- Calculate the effective rate and total dollars for each complete scenario.
Which model tends to fit which shop?
A mobile mechanic taking a handful of cards may happily pay for the simplicity of flat rate. A larger shop with steady systems and an owner who reads statements may get more from interchange plus. A high-ticket independent shop with heavy credit volume and disciplined advisors may be a strong dual-pricing candidate.
Those are places to begin, not rules carved into a terminal. We have to look at the shop's transactions, people, and workflow before the pricing model has a meaning.
Questions business owners ask
Is interchange plus always cheaper than flat rate?
No. It is usually more transparent, but the final cost depends on card mix, markup, transaction count, fixed fees, and payment channels.
Is dual pricing always the cheapest for the shop?
Not always. Remaining fees, debit mix, customer payment changes, integration work, and customer impact all affect the result.
How can I compare proposals with different fees?
Apply every proposal to the same transaction data, include all recurring and event fees, then compare total dollars and effective rate.
Primary sources
BlueFinch reviewed these sources on August 11, 2026. Payment rules and state requirements can change.
- Visa: Credit Card Processing Fees and Interchange Rates
- Chase Payment Solutions: Understanding Your Processing Statement
This page provides general business information, not legal, tax, or accounting advice.