Why interchange-plus wins once you are big enough
Every card sale carries interchange, the fee the card-issuing bank sets, plus a smaller network fee to Visa or Mastercard. A flat-rate processor charges you one price that covers all of it, plus its margin. Interchange-plus passes those wholesale costs through at cost and adds a fixed markup you can see on your statement.
The wholesale cost swings a lot by card. A regulated debit card from a big bank costs 0.05% + 21¢ on Visa, while a Visa Infinite rewards card costs 2.30% + 10¢ in person [9]. A flat rate charges both the same. On interchange-plus, your debit-paying customers cost you far less, and at volume that adds up to thousands a year.
The trade-off is that interchange-plus statements are longer and the total moves month to month with your card mix. That is why the markup must be published and fixed in writing. All three leaders on this list publish theirs [1][2][3].
Network fees: the line most cost comparisons skip
Card network fees, also called assessments, are charged on every interchange-plus sale. Most comparisons leave them out, which flatters interchange-plus. Dharma is unusual in printing them: its restaurant page shows a Visa assessment of 0.14% + 2¢ and a Mastercard assessment of 0.12% + 2¢ on a $25 sale [4].
Using the Visa figure for every sale, network fees add about $165 a month at $75,000 and $330 a month at $150,000 on $25 tickets. The table above includes them. Even with them in, the best interchange-plus account we priced costs about $1,188 a month less than Square's standard rate at $150,000, or roughly $14,250 a year.
Watch for padded pass-through
Some processors call themselves interchange-plus but add their own fees on top of network fees, or mark up interchange itself. Ask for a fee schedule that lists every line, and compare your first statement's interchange lines against the card networks' published tables.
How we ranked high-volume processors
The order is our overall score from the six weighted criteria on our methodology page, the same as every processor review: holds and termination risk 25%, pricing transparency 20%, contract terms 20%, total cost 15%, support 10% and customer evidence 10%. Dharma (3.875) and Stax (3.85) both round to 3.9, so the unrounded score breaks the tie.
We included only providers with a published interchange-plus price or a stated custom-pricing path for volume. Square's 3.2 places it sixth; BatchOut, our processing service, earns money on Square sign-ups, and that did not change its position. We left out GoDaddy Payments, PayPal and Shopify here because their published pricing is flat-rate, though GoDaddy invites businesses over $100,000 a year to call for offers [10].
Which one fits your size and ticket
| Your business | Lowest of the three | Why |
|---|---|---|
| $50,000 to $100,000 a month, small tickets | Dharma | 0.15% markup, $20 fee [1] |
| Over $100,000 or 5,000 sales a month | Dharma | Drops to 0.10% + 8¢ [4] |
| Over about $180,000 a month | Stax | A fixed $199+ fee beats a 0.10% markup [2][4] |
| Volume that swings by season | Helcim | Tier set from your last three months [3] |
Dharma and Stax charge the same 8¢ per sale, so the race between them comes down to Dharma's 0.10% markup against Stax's fixed membership [4][2]. Dharma's $20 monthly fee narrows the gap to $179. Once 0.10% of your monthly sales passes $179, which happens at about $179,000 a month, Stax's published price is lower, as long as its $199+ tier holds at $199. Below that, Dharma wins at any ticket size. Bigger tickets do not change this, because both charge the same per-sale fee.
Switching at high volume without a hold
A new processor sees a high-volume account arrive all at once, and that is exactly what triggers risk reviews. Plan the switch.
- Send three to six months of statements with the application so the new processor sees your normal volume and refund rate.
- Ask in writing whether a reserve will apply, and on what terms. Dharma's posted bank program guide, for example, lets a reserve be held for at least ten months after closing [11].
- Run both accounts in parallel for a few weeks before moving all volume.
- Keep the old account open until its chargeback window passes.
Our how to switch processors guide covers notice letters and equipment, and our interchange-plus vs flat rate explainer shows how to read the new statement.