What is an interchange fee in ecommerce? The hidden layer inside your 2.9%

An interchange fee is the slice of every card transaction that the card-issuing bank keeps. It is set by the card network (Visa, Mastercard, Discover), not by your processor, and it is the single largest layer inside the 2.9% + $0.30 you pay Stripe or Shopify Payments. For a typical US online consumer credit transaction in 2026, interchange runs 1.89% to 2.50% + $0.10 (Visa CPS/e-Commerce Basic up through Signature Preferred) before assessments and processor markup get added on top.

For an ecom operator, interchange is the line nobody breaks out on your Stripe statement and the reason your "2.9% flat rate" never actually clears at 2.9%. On a $100 US online credit transaction, roughly $1.75 goes to the issuing bank as interchange, $0.13 goes to Visa or Mastercard as assessments, and $1.32 is processor markup (the part Stripe keeps). Once you cross roughly $1M/month in card volume, you can move from flat-rate (2.9%) to interchange-plus pricing and capture the 50 to 80 bps of margin Stripe is currently keeping as markup. At $10M/year in card volume, that move is worth $50,000 to $80,000/year. At $50M/year, it is $250,000 to $400,000. The same logic applies on the Shopify Plus rate review where the negotiated floor we have seen on real 2026 deals is 1.15% + $0.15. Numbers below are US Visa, Mastercard, Discover global rules; AU (eftpos), CA (Interac), and EU (IFR-capped 0.2%/0.3%) all differ at the network layer.

How it works

Three layers stack inside every flat-rate processing fee. The first and largest is interchange, paid by the merchant's processor to the card-issuing bank. The network (Visa, Mastercard, Discover) publishes the rate table and updates it twice a year, typically in April and October. The rate depends on card type (credit vs debit), card tier (basic, rewards, premium, premium-plus), and acceptance environment (card-present vs card-not-present, with CNP rates higher because online fraud risk is higher). For US online consumer credit, Visa CPS/e-Commerce Basic clears at 1.89% + $0.10; Visa CPS/e-Commerce Rewards Signature Preferred clears at 2.50% + $0.10. Mastercard Merit I CNP runs 1.95% to 2.60% + $0.10. Discover CNP runs 1.89% to 2.40% + $0.10.

The second layer is the network assessment fee, paid to Visa or Mastercard directly. Visa assesses 0.14% on credit volume; Mastercard assesses 0.1375% on most volume. This is the smallest layer (about $0.13 on a $100 sale) and is non-negotiable.

The third layer is processor markup, which is where Stripe, Shopify Payments, and PayPal make their money. On flat-rate 2.9% + $0.30 pricing, the processor charges you the same number regardless of which card the customer used. If the customer pays with a basic card (1.89% interchange), Stripe keeps more. If the customer pays with a premium rewards card (2.50% interchange), Stripe keeps less. On interchange-plus pricing, the markup is broken out separately (for example, "interchange + 0.30% + $0.15") and you pay actual interchange directly. Above $1M/month, that switch usually saves 50 to 80 bps. Regulated US debit is capped much lower than credit under the Durbin amendment: $0.21 + 0.05% + $0.01 fraud adjustment through June 30, 2025, then $0.144 + 0.04% + $0.013 effective July 1, 2025 under the finalized Fed rule. Only debit cards from banks with $10B+ in assets fall under the cap; smaller-issuer debit is uncapped.

Common triggers

• Card tier mix shifts: when your customers swap basic Visa for premium-rewards travel cards, your effective rate rises 30 to 60 bps with no change in your contract. On flat-rate pricing you do not see it; on interchange-plus it is the line item.
• Cross-border transactions: international cards add an interchange surcharge (often 0.4% to 1.0%) plus a network cross-border assessment. A US merchant taking a UK-issued card pays meaningfully more than a US-issued one.
• Card-not-present vs card-present: online (CNP) interchange runs 30 to 60 bps higher than in-store. If you operate both an ecom site and a pop-up, the same card costs you more online.
• Amex blend: Amex sets its own rate (typically 2.5% to 3.5% all-in) and does not use the Visa/Mastercard interchange tables. A higher Amex share inside your customer mix raises your effective rate.
• Crossing the $1M/month volume line: Stripe begins offering interchange-plus around $1M/month; Adyen prices enterprise interchange++ from the start. At $10M+/month, custom interchange-plus is standard.
• Surcharging or cash-discounting: some US states let you pass card fees through to the customer (subject to network caps, typically 4%). The economics on flat-rate vs interchange-plus look very different once you do this.

The most common mistake

The biggest mistake operators make is renewing flat-rate 2.9% pricing when they have crossed the volume threshold to negotiate interchange-plus. Stripe will quote it if you ask above roughly $1M/month, but you have to ask. At $10M/year in card volume, the move from 2.9% flat to interchange-plus typically saves 50 to 80 bps, or $50,000 to $80,000 a year. At $50M/year, it is $250,000 to $400,000. The second mistake is treating the 2.9% number as the full cost; the all-in effective rate after premium-card mix, cross-border, and Amex blend is usually 3.1% to 3.5% on a US DTC book. Pull your last 90 days of processing statements, divide total fees by total card volume, and compare to 2.9%. Anything over 3.0% is grounds for a rate review. The third mistake, common on Shopify Plus, is paying both Shopify Payments processing AND the third-party gateway fee (0.15% to 0.50%) because checkout is still routed through a non-Shopify gateway. Audit your gateway-and-processor stack before your next renewal. The negotiated floor we have seen on real 2026 Plus deals is 1.15% + $0.15 per transaction, roughly 100 bps below rack.

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