Normalize processor quotes before comparing the headline rate

Two processor quotes are not comparable merely because each contains a percentage and a transaction fee. One may blend network costs and markup into one rate. Another may pass through variable interchange and network charges, then add its own markup. Normalize both against the same transaction mix before deciding.

Stripe’s provider explanation separates interchange-plus into issuer interchange, network fees, and processor markup; it describes blended pricing as one provider-set rate. Square’s current support page is a provider-specific example of a blended rate that varies by acceptance channel and is deducted before payout. Neither page establishes the best model for every merchant. They establish why the labels must be unpacked (Stripe; Square).

Build one input sheet

Use a recent representative month, not the best week. Record gross card volume, transaction count, average ticket, refunds, disputes, and the share of in-person, online, keyed, international, and card-on-file payments. If the interchange-plus quote includes rate tables, separate debit, basic credit, rewards, commercial, and other categories that materially affect the business. When the quote omits a cost, mark it “unknown”; do not silently enter zero.

Ask each provider to price that exact mix. Collect every fixed charge: monthly platform, gateway, statement, PCI program, terminal rental, minimum, account updater, tokenization, dispute, refund, batch, and early-termination charges. Record whether fees are returned after a refund. Then note payout timing and reserves separately. Faster access to money is valuable, but it is not a processing-fee discount. The merchant payout reconciliation guide shows how deductions become a bank deposit, while reserves and negative balances separates available cash from sales.

A hypothetical worked comparison

Assume an anonymous shop processes 1,000 transactions totaling $50,000 in one month. Quote A is blended at 2.75% plus $0.10 per transaction, with no monthly fee:

• percentage charge: $50,000 × 2.75% = $1,375
• transaction charge: 1,000 × $0.10 = $100
• normalized monthly cost: $1,475
• effective rate: $1,475 ÷ $50,000 = 2.95%

Quote B is interchange-plus. For comparison only, suppose the shop’s actual mix produces $950 of interchange and $70 of network fees. The processor adds 0.35% plus $0.08 per transaction and a $25 monthly fee:

• pass-through interchange: $950
• pass-through network fees: $70
• processor percentage: $50,000 × 0.35% = $175
• processor transaction charge: 1,000 × $0.08 = $80
• monthly fee: $25
• normalized monthly cost: $1,300
• effective rate: $1,300 ÷ $50,000 = 2.60%

In this hypothetical month, B costs $175 less. That is not a market quote, savings promise, or forecast. If the card mix makes interchange $1,150 rather than $950, B rises to $1,500 and becomes $25 more expensive than A. The comparison turns on actual mix and complete fees, not on the smaller advertised markup.

Stress the assumptions

Recalculate at low, ordinary, and high sales months. Change average ticket while holding volume constant: a per-item charge weighs more heavily on small tickets. Raise the card-not-present or premium-card share. Add the realistic dispute and refund count. Include hardware and software subscriptions over a sensible contract period, but keep one-time equipment purchases visible rather than hiding them in a monthly rate.

Finally, compare contract language: which charges can change, which pass-through costs change automatically, what reporting exposes each component, and how long data can be exported after termination. Ask the interchange-plus provider for a sample statement showing qualification categories. Ask the blended provider which channels trigger different rates. A quote is ready for approval only when another person can reproduce the total from written assumptions.

Sources

• Stripe, Interchange plus pricing explained — provider-specific
• Square, Learn about Square fees — provider-specific