Why interchange-plus pricing cannot be totaled
Three US providers publish a markup on interchange and not the interchange itself. Interchange is the larger part of the price, so no total exists, and the effective-rate column for those plans stays empty on purpose.
The cheapest-looking pricing on the site is the pricing I cannot rank. That is not a paradox, and it is not an accusation. It is what happens when a provider publishes its own margin honestly and the cost underneath that margin belongs to somebody else.
What the three providers actually publish
Helcim publishes "interchange + 0.40% + 8c" for card-present sales, falling to interchange plus 0.35% and $0.07 above $50,000 a month (checked 2026-08-25). Stax publishes "$99/month with 0% markup on direct-cost interchange" plus $0.08 per card-present transaction (checked 2026-08-25). Payment Depot publishes "0% markup on interchange" and "variable rates as low as 0.2% - 1.95%", with the same $0.08 card present (checked 2026-08-25).
| Provider | Published card-present markup | Per sale | Monthly | Effective rate |
|---|---|---|---|---|
| Helcim, $0 to $50,000 a month | interchange + 0.40% | $0.08 | $0 | not computable |
| Helcim, $50,000 to $100,000 a month | interchange + 0.35% | $0.07 | $0 | not computable |
| Stax, up to $150,000 a year | 0% markup on interchange | $0.08 | $99 | not computable |
| Payment Depot membership | 0% markup on interchange | $0.08 | not published | not computable |
^ Each provider's own pricing page (checked 2026-08-25). Payment Depot's "0.2% - 1.95%" is its own wording for a range of interchange rates, not a price for a plan.
Read the table again and notice what is missing from every row. There is no first term. "Interchange + 0.40%" is an addition with one number supplied.
Why can a published markup not be added up?
Because interchange is set by the card networks, varies by card type and by merchant category, and appears on none of the three pricing pages (checked 2026-08-25). It is also the larger part of the two. Adding a markup to an unknown gives an unknown, so the site prints the markup, marks the plan not computable, and leaves it out of every ordering.
Five plans across the 22 US providers I hold are priced this way (checked 2026-08-25). Only 7 of those 22 publish enough to compute a total at all. Those five plans are not the worst deals in the provider list. They are the ones a comparison table cannot honestly sort.
What a flat rate does instead
One number covers everything. Square's US Free plan is 2.60% plus $0.15 in person, and that percentage is the whole of what Square takes, interchange included (checked 2026-08-25). Take $25,000 of card sales a month, at the site's assumed average sale of $25.00. That is $800 a month, $28,800 over three years, and an effective rate of 3.20%.
SumUp's UK Tap to Pay plan publishes 1.69%, with no per-item fee and no hardware (checked 2026-08-25). At £25,000 a month that is £422, and £15,210 over three years. Both totals hold because nothing was left outside them.
Work out your own effective rate for any plan on the site that has one. The box stays empty for Helcim, Stax, and Payment Depot, whatever you type into it. What card payments cost sets out the same formula in full.
Is interchange plus cheaper?
It depends on your card mix, and the published numbers show why no page can settle it. Helcim's card-present markup of 0.40% plus $0.08 is a small fraction of Square's 2.60% plus $0.15 (checked 2026-08-25). Square's 2.60% has to cover interchange out of itself, so the comparison is between one provider's whole take and another provider's margin alone.
Whether the sum comes out lower depends on your card mix, which is exactly the thing nobody publishes. A till full of premium rewards credit cards carries higher interchange than a till full of debit. Helcim's markup also falls as volume rises, from 0.40% to 0.35% above $50,000 a month (checked 2026-08-25). Square's Free plan does not move: the published 2.60% is the same at every volume, and the effective rate holds at 3.20% from $2,000 to $100,000 a month. A flat rate is a ceiling and a floor at once. Interchange plus is a floor with the ceiling unstated.
This is a limit of public information, not a fault of the provider
Helcim publishes a $0.00 monthly fee, a $0.00 PCI fee, a $0.00 monthly minimum, and no contract term (checked 2026-08-25). That is more disclosure than most of the 22 US providers manage. One of the 22 publishes no rate at all, and two more have pricing pages I could not read (checked 2026-08-25). Ranking Helcim lower than Square for being unrankable would punish the wrong behavior.
Stax publishes $99.00 a month up to $150,000 a year and $139.00 a month from $150,000 to $250,000, with a SwipeSimple B350 reader at $125.00 (checked 2026-08-25). Payment Depot does not publish its membership fee at all (checked 2026-08-25). That last gap is a different problem from the interchange gap: the membership fee is Payment Depot's own number, and it could be printed.
What to do with a plan you cannot total
Ask for a statement analysis in writing, in the same shape as the published price. Ask what the markup is on debit and on credit separately. Ask what the monthly fee is, and whether the reader is bought or rented. Ask what happens to the markup if your volume falls back below a tier. What the headline rate leaves out lists the charges that survive every pricing model, and who publishes a card rate, and who does not sets out how much of a price each provider will put on a page.
Then read the two provider pages side by side. Helcim's page shows a published markup and an empty rate column; Square's page shows a filled one. The difference between them is not quality. It is how much of the price the company is in a position to publish.
Where the answer changes
- If your card sales are well above $50,000 a month, the markup tiers start to matter more than the flat rate, and a statement analysis from an interchange-plus provider is worth the effort of collecting three months of statements.
- If you take small sales and few of them, the $0.08 per transaction and the $99.00 monthly fee land harder than any percentage, and a flat-rate plan with no monthly fee is easier to budget.
- If you have no statements yet because the shop has not opened, do not decide yet. Nobody can price interchange plus for a till whose card mix does not exist, and a flat rate you can total is the safer starting point.
Who this article is not for
This is not for a merchant who has already been quoted a full interchange-plus schedule in writing. If you hold a rate sheet with the interchange categories on it, you have the number this article says is missing. Add it up rather than read about why I cannot. This article is also not a recommendation against Helcim, Stax, or Payment Depot, none of which I have used.
Sources
- Helcim pricing page, https://www.helcim.com/pricing/, checked 2026-08-25
- Stax pricing page, https://staxpayments.com/pricing/, checked 2026-08-25
- Payment Depot pricing page, https://paymentdepot.com/pricing/, checked 2026-08-25
- Square pricing page, https://squareup.com/us/en/pricing, checked 2026-08-25
- SumUp UK card readers page, https://www.sumup.com/en-gb/card-readers/, checked 2026-08-25
How this article was made. Written by Kaz, an independent publisher. All figures come from the companies' own published documentation; each figure carries the date it was last checked. I have not used these products, and nothing here is a personal test result. The arithmetic is shown so you can recalculate with your own numbers. Found an error? Use the contact form; corrections are logged on the Editorial policy page.
Related articles
- The three numbers behind a card rate
- What a 'get a quote' button is for
- What the headline rate leaves out
Written by Kaz (pen name). Figures are copied from providers' published pricing pages on the dates shown. We have not used these products. Corrections: contact form.