TL;DR
Interchange-plus pricing passes the Visa or Mastercard wholesale fee straight through and adds a fixed processor markup on top. At $250K monthly card volume, the right interchange-plus plan saves 0.30 to 0.60 percent versus flat-rate Stripe or Square. Helcim wins for $25K to $250K monthly. Stax and Payment Depot win above $50K once the membership math clears break-even. Worldpay wins above $5M monthly with a negotiated deal. Skip interchange-plus if you process under $10K monthly. The fixed monthly cost erases the rate savings at that tier.
How we ranked
We scored each processor on six criteria with explicit thresholds:
- Effective rate at $250K monthly volume on a 70/30 card-present and card-not-present mix.
- Contract length and early termination fee. We penalize anything over 12 months without a no-fee out clause.
- Settlement speed counted in business days from batch close to bank deposit.
- Level 2 and Level 3 data support. This matters if more than 15 percent of your volume is B2B or government cards.
- Hardware lock-in. Closed-ecosystem terminals raise your switching cost.
- Public pricing. If the markup is not on the website, we treat that as a yellow flag.
We pulled interchange categories from the Visa Interchange Schedule and Mastercard Interchange Rates and Criteria, both publicly published quarterly. Processor markups came from each provider's public pricing page or 10-K. We did not score sales-pitch features like advanced reporting or AI dashboards. Operators pay for the rate, the contract, and the settlement window.
At a glance
Quick comparison at $250K monthly volume on a mixed card-present and online retail profile. All rates pulled from each provider's public pricing page.
| Provider | Headline pricing | Contract | Settlement | Best for | Watch out for |
|---|---|---|---|---|---|
| Helcim | IC + 0.40% + $0.08 in-person | None | 2 days | $25K to $250K monthly | Limited international |
| Stax | $99/mo + IC + $0.08 in-person | Month-to-month | 1 to 2 days | $50K to $500K monthly | Fixed cost under $40K |
| Payment Depot | $79 to $199/mo + IC + $0.05 to $0.15 | Month-to-month | 2 days | $100K+ subscription model | Tier locks features |
| Stripe (custom) | IC + custom % (request) | Custom | 2 days | $1M+ annual online | Standard plan is flat 2.9% |
| Worldpay | IC + custom (sales) | 12 to 36 months typical | 1 day | $5M+ enterprise | ETF on early exit |
Helcim
Helcim publishes interchange-plus rates on its website, which is rare in this industry. The card-present markup is 0.40 percent plus 8 cents, and online is 0.50 percent plus 25 cents per the published pricing page. Automatic volume discounts kick in at $25K, $50K, $100K, and $250K monthly tiers. There is no monthly fee, no statement fee, no PCI fee, and no contract.
At $100K monthly card-present volume with a typical retail card mix where Visa CPS Retail interchange runs 1.50 to 1.80 percent per the Visa schedule, your blended effective rate lands around 1.95 to 2.30 percent. That is roughly 0.30 to 0.40 percent below Square's flat 2.6 percent plus 10 cents at the same volume.
Who it's for: SMB retail, restaurant, and professional services at $25K to $250K monthly volume that wants pricing transparency without a sales-call negotiation.
Who should avoid it: high-risk verticals like CBD, firearms, and nutraceuticals, and merchants who need a dedicated account manager. Helcim's support is solid but it is not white-glove enterprise. International acceptance is also narrower than the large acquirers.
Hardware: the Helcim Smart Terminal is $329 with no monthly device fee. The terminal is locked to Helcim processing, so you cannot reuse it if you switch. Funding is 2 business days standard.
Stax
Stax (formerly Fattmerchant) charges a flat $99 per month subscription on its core plan, then passes interchange straight through with a $0.08 markup on in-person transactions and $0.18 on online transactions per the public pricing page. There is no percentage markup over interchange on the base plan.
The math at $50K monthly volume with an $80 average ticket (625 transactions): per-transaction markup totals $50, plus the $99 subscription. Total markup: $149, or 0.30 percent effective. At $200K monthly with 2,500 transactions: $200 plus $99 equals $299 markup, or 0.15 percent effective. The model breaks even with Helcim somewhere around $40K to $50K monthly. Below that tier, you are paying for capacity you do not use.
Who it's for: $50K to $500K monthly retail, e-commerce, or B2B that wants subscription-style pricing and predictable monthly cost.
Who should avoid it: low-volume merchants under $40K monthly. The subscription is dead weight at that tier. Hardware: Stax integrates with most third-party terminals and POS systems including Clover, so there is less hardware lock-in than Helcim. Funding is 1 to 2 business days, and phone support runs 24/7.
Payment Depot
Payment Depot uses a membership model: $79 to $199 per month depending on tier, then interchange plus 5 to 15 cents per transaction per the public pricing page. There is no percentage markup over interchange.
The math at $100K monthly card-present volume with 1,250 transactions: the $99 mid-tier plan plus $0.10 per transaction equals $99 plus $125, or $224 total markup. That is 0.22 percent effective on top of interchange. At $300K monthly with 3,500 transactions: $99 plus $350 equals $449, or 0.15 percent effective.
Who it's for: $100K+ monthly volume retail, food service, and B2B that wants the lowest possible per-transaction cost and is comfortable with U.S. business-hours support only.
Who should avoid it: 24/7 operations that need overnight support, and businesses with high ticket counts but low average ticket size. The per-transaction fee compounds against you when the average ticket is under $20.
Contract: month-to-month with no long-term lock-in. Payment Depot is owned by Stax and runs on the same processing back-end, so reliability and settlement behavior mirror Stax. Hardware is agnostic. You can bring your own EMV terminal or buy one through Payment Depot at near-cost, which is a meaningful saving versus closed ecosystems. Funding is 2 business days standard.
Stripe (custom interchange-plus)
Stripe's published plan is flat-rate at 2.9 percent plus 30 cents online and 2.7 percent plus 5 cents in-person. That is not interchange-plus. For higher-volume merchants, Stripe offers a custom interchange-plus deal, typically negotiated above $1M annual processing volume, though it is not on the public page and requires a sales conversation.
At $250K monthly online volume with a typical e-commerce card mix, Stripe's flat-rate plan runs roughly 0.50 to 0.70 percent above what a negotiated IC+ deal would cost. That is $15,000 to $21,000 per year you could recover by moving to the negotiated rate.
Who it's for: $1M to $50M annual online merchants who want Stripe's developer tooling, broad currency support, and global card acquiring, and who are willing to negotiate.
Who should avoid it: cost-sensitive SMB merchants under $1M annual, where Stripe will not negotiate and the flat rate eats the margin. Also avoid for in-person-heavy retail. Stripe Terminal is functional but the surrounding POS ecosystem trails Square and Clover.
Worldpay
Worldpay does not publish flat-rate pricing. Every deal is interchange-plus or interchange-plus-plus, negotiated with a sales representative, with markups that depend on volume, vertical, and contract length.
For $5M+ monthly volume merchants, Worldpay typically offers card-present markups in the 0.05 to 0.15 percent range plus 3 to 7 cents, and online in the 0.15 to 0.30 percent range plus 7 to 10 cents. These are negotiated and not guaranteed without a signed contract. Worldpay's parent FIS sits among the largest U.S. acquirers by purchase volume per the Nilson Report.
Who it's for: $5M+ monthly enterprise merchants, multi-location retail and hospitality, and complex B2B with level 3 data and large-ticket settlement needs.
Who should avoid it: anyone under $1M monthly. Worldpay contracts typically run 12 to 36 months with early termination fees of $250 to $500, and the sales process is slow. SMB merchants get better economics from Helcim, Stax, or Payment Depot.
Hardware is open and integrates with most terminals and POS systems. Funding is 1 business day standard, with same-day available on enterprise contracts.
Verdict
For $25K to $250K monthly volume, Helcim wins. Public pricing, no contract, no monthly fee, and a published markup competitive with anything else at that tier.
For $50K to $500K monthly volume, Stax and Payment Depot both win on the math once you clear the $40K to $50K break-even. Choose Stax if you want 24/7 support and integrated software. Choose Payment Depot if you want the lowest per-transaction cost and don't mind business-hours support.
For $1M+ annual online volume, request Stripe's custom interchange-plus desk. The flat-rate plan is leaving money on the table at that volume per the public pricing page.
For $5M+ monthly enterprise, Worldpay or another large acquirer makes sense. The negotiated markup at scale beats any SMB plan, and the Federal Reserve payments studies show that card payment volume continues to grow, so locking in a sub-10 basis point markup at this tier compounds over the contract term.
Skip interchange-plus entirely if you process under $10K monthly. The fixed monthly cost in any membership model erases the rate savings, and a flat-rate provider is simpler and cheaper at that volume.
