Interchange Plus vs Flat Rate Pricing: Which Costs Less?

Interchange plus vs flat rate pricing comes down to volume and card mix. Flat rate charges one fixed percentage plus a fixed fee on every sale, which is simple and predictable. Interchange plus passes through the card network's actual cost and adds a small fixed markup, which is usually cheaper once you process roughly $50,000+ a month.

Most store owners never choose. They sign up for Stripe, PayPal or Shopify Payments, accept the default rate, and never look again. That's fine at $2,000 a month. At $80,000 a month, it can quietly cost you thousands a year. This guide shows you the math, the break-even point, and the exact moment to move.

Flat Rate vs Interchange Plus: How Each Model Works

Flat rate bundles every cost into one price. Interchange plus splits the price into three layers you can see: interchange, the card network's assessment, and the processor's markup.

Flat rate payment processing

With flat rate payment processing, you pay the same percentage on every transaction regardless of card type. Stripe's standard US pricing, listed on stripe.com/pricing, is 2.9% + $0.30 for online card payments. PayPal and Square use similar structures with slightly different numbers.

The processor takes on the risk that your customers pay with expensive cards. In exchange, you get no surprises, no statement decoding, and approval in minutes.

Interchange plus pricing explained

Interchange plus pricing explained in one line: you pay the real wholesale cost of each transaction, plus a fixed markup. Every card payment involves three parties charging you:

• Interchange: set by Visa and Mastercard, paid to the card-issuing bank. It varies by card type, and it's the largest piece.
• Network (assessment) fees: small percentages paid to Visa, Mastercard and others.
• Processor markup: the part you negotiate, for example 0.30% + $0.10.

Visa and Mastercard publish their interchange schedules, and both are reachable from usa.visa.com and mastercard.us. A basic consumer debit card might cost you around 0.8% in interchange. A premium rewards credit card can run past 2%.

Blended vs interchange pricing

You'll also see tiered or "blended" quotes. Blended vs interchange pricing is mostly a transparency question. Blended pricing averages costs into one or two rates (flat rate is the extreme version). Tiered pricing sorts transactions into "qualified," "mid-qualified" and "non-qualified" buckets, and processors decide which bucket applies. That's the least transparent model, so avoid it unless the rate is clearly lower.

Which Is Cheaper? A Real Cost Comparison

Interchange plus is cheaper when your average card costs less than the flat rate assumes, and when your volume is high enough to negotiate a small markup. Below that, flat rate usually wins on total effort and often on price.

Here's an example. Say you sell $100,000 a month across 1,500 orders (a $66.67 average order). The interchange-plus quote below is illustrative, not a published rate, so your actual numbers will differ.

Model	Rate	Monthly fees	Effective rate
Flat rate (Stripe standard)	2.9% + $0.30	$2,900 + $450 = $3,350	3.35%
Interchange plus (illustrative)	~1.8% blended interchange + assessment, plus 0.30% + $0.10	$1,800 + $300 + $150 = $2,250	2.25%
Monthly difference		$1,100	$13,200 per year

Now shrink the same store to $5,000 a month. Interchange plus might save you $50 to $80, but many interchange-plus providers charge monthly fees, PCI fees, or minimums. Those can erase the gain. Your card mix matters too: a store selling mostly to US consumers using debit cards benefits more than one with lots of international or corporate cards, which carry higher interchange.

Payment processing cost calculator: do it yourself

You don't need a fancy payment processing cost calculator. A spreadsheet works:

1. Pull 3 months of processing statements and total your sales volume and transaction count.
2. Calculate your current effective rate: total fees ÷ total volume.
3. Ask a prospective processor for its interchange-plus markup and any monthly fees.
4. Estimate interchange at 1.7% to 2.0% for a typical US online mix, then add the markup and fixed fees.
5. Compare annual totals, not just percentages.

If you want a real number rather than an estimate, ask the processor to run a statement analysis on your actual card data. Reputable ones do it free.

When to Switch Payment Processors

Switch when the annual savings clearly beat the cost and hassle of moving. A practical rule: consider interchange plus once you process $50,000 to $80,000 a month and your effective rate sits above 3%.

Watch for these signals in your own numbers:

• Your effective rate is above 3% on a US-heavy customer base.
• Your average order is over $100. The fixed $0.30 matters less, but the percentage hits harder, and interchange plus saves more on larger tickets.
• You're growing fast. A deal negotiated at $30,000 a month is worth far more at $150,000.
• You have lots of debit and low-cost cards. Flat rate overcharges you for these.
• Your flat-rate processor is holding funds or raising reserves. Stability is worth money too. See our guide on handling chargebacks as an online store owner, since dispute rates affect your pricing leverage.

Don't switch for micro-savings. If you'd save $300 a year and spend a weekend migrating, stay put. Also check whether your platform locks you into its own gateway. On Shopify, using an outside gateway adds a penalty, which we break down in Shopify third party payment gateway fee. That penalty can cancel any interchange-plus gain.

How to Negotiate Payment Processing Rates

You can negotiate rates once you have volume and statements to prove it. Processors expect it, and the first quote is rarely the floor.

Steps that work

1. Collect competing quotes. Get at least three written interchange-plus quotes. Include monthly fees, PCI fees, chargeback fees and early termination terms.
2. Negotiate the markup, not the headline. A markup of 0.20% to 0.40% plus $0.05 to $0.15 per transaction is a realistic target for mid-size online merchants, though it varies by risk and volume.
3. Ask about hidden line items. Gateway fees, batch fees, statement fees, and annual fees all add up.
4. Avoid long contracts. Month-to-month is better than a three-year deal with a $500 cancellation fee.
5. Use your clean history. Low refunds, low disputes, and steady growth are your leverage.

Stripe custom pricing

Stripe custom pricing exists, and it's the easiest first move because you don't have to change processors. Stripe's pricing page notes that businesses with large volume or unusual needs can contact sales for custom packages, which can include interchange-plus pricing. Stripe doesn't publish a volume threshold, so treat anything you read elsewhere as a guess. Reach out with your 3-month volume, average order size, and card mix. If they won't move, you've at least got a baseline for other quotes.

Platform fees stack on top of all this. If you're on a hosted platform, read how Shopify payment gateway charges and Shopify Payments fees by plan work before you assume a processor deal is your only cost lever.

Is There a Lowest Fee Payment Gateway?

No single lowest fee payment gateway exists for every store. The cheapest option depends on your volume, average order value, card mix, and platform fees. For small stores, flat rate from Stripe or PayPal is usually cheapest after you count your time. For larger stores, interchange plus nearly always wins.

Compare candidates on these points, not on the headline percentage:

• Total effective rate on your own last three months of sales.
• Platform surcharges when you use a non-native gateway.
• Payout speed and reserve or hold policies.
• International and currency conversion fees, which can add 1% or more.
• Dispute fees, often $15 or more per chargeback.

For side-by-side numbers, see our comparisons of Stripe vs Square for an online store and the best payment gateway for a small online store. If you run WooCommerce, the WooCommerce payment gateway comparison covers the plugin-level fees.

Common questions

Is interchange plus always cheaper than flat rate? No. At low volume, monthly fees and minimums can make it more expensive. At higher volume it's usually cheaper because you stop overpaying on low-cost cards.

Can I use interchange plus with Stripe? Yes, through Stripe's custom pricing for qualifying businesses. You'll typically need to contact Stripe's sales team.

Do interchange rates change? Yes. Visa and Mastercard update their fee schedules, usually in April and October, so your costs can shift even if your markup stays the same.

Picking the Right Model for Your Store

Choose flat rate if you process under about $30,000 a month, value predictability, and don't want to read statements. Choose interchange plus if you're above $50,000 a month, your effective rate tops 3%, and you're willing to review a more detailed statement.

Between $30,000 and $50,000, run the spreadsheet. Either answer can be right.

Payment fees are only one line in your cost stack. Platform subscriptions, app fees and transaction commissions often add more. Rovela runs a single flat subscription with no commission on sales, and Stripe checkout is built into every store, so your processing rate is the only variable left to optimize. You can see the plan details on the pricing page, or describe your store and see it built to find out how it works before committing to anything.