Subscription-based payment processing with interchange-plus pricing
Stax (formerly Fattmerchant) is a US payments processor that sells a subscription model: you pay a flat monthly fee and Stax passes interchange through at cost plus a small per-transaction surcharge, with no percentage markup. We picked it because for a merchant doing $8k/month or more in card volume, switching from Square or Stripe to Stax can cut effective rates by 30-50%, and the maths gets better as volume grows.
You sign a merchant agreement, complete underwriting, and Stax provisions a merchant account through their processor partners. Pricing is interchange-plus: card networks (Visa, Mastercard, Amex, Discover) charge their interchange and assessment fees directly, Stax adds a fixed per-transaction fee (typically 8-15c), and you pay a monthly platform fee. There is no percentage markup on volume.
The Stax platform includes a virtual terminal, online payments, invoicing, recurring billing, contactless payments, ACH and a reporting dashboard. Hardware (chip and contactless terminals) is sold or rented separately.
Stax is sold by quote, but published indicative pricing is roughly: $99/month for under $250k annual volume, $159/month for $250k-500k, $199/month for $500k+, plus 8-15c per transaction and pass-through interchange. Total effective rate at typical card mix lands around 1.8-2.1% for in-person, comparable for online. Compare to Square at 2.6% + 10c and the savings appear above ~$8-10k/month in card volume. Some plans require a 3-year term with early termination fees; ask explicitly.
| Platform | Strength | Weakness vs Stax |
|---|---|---|
| Stax | Subscription pricing, no percentage markup | — |
| Square | Free monthly, free hardware | Higher per-transaction rate above $8k/month |
| Helcim | Similar interchange-plus, no monthly fee | Less mature platform features |
| Stripe | Best developer experience | 2.9% + 30c online is expensive at scale |
Buy if you process more than ~$8k/month in cards in the US, you have stable predictable volume, and you are tired of paying flat percentages to Square or Stripe that scale with your revenue. Run the maths against your actual interchange mix before committing.
Skip if you are a low-volume merchant under $5k/month (Square or Stripe will be cheaper after the monthly fee), or you need international coverage outside the US (Stax is US-only).
Click through the verified link for a custom quote. We re-check the offer monthly.
Agencies sending 50–500 invoices monthly benefit from Stax's bundled invoicing and flat-rate processing. A $50K project invoice costs the same to process whether it's $500 or $50,000, eliminating percentage-based leakage. Stax handles recurring retainers and one-time projects without switching platforms.
SaaS teams with predictable MRR use Stax to manage subscription cycles, failed-payment recovery, and prorated upgrades. The platform auto-retries failed cards and sends dunning emails, reducing churn from payment friction. Founders avoid Stripe's complexity and Chargebee's per-subscription markup.
Consulting firms, law practices, and design studios benefit most from Stax's flat-rate model. A $100K contract costs the same to process as a $10K one. Stax handles variable invoicing without the percentage bleed that eats into margins on premium engagements.
Quarterly access to product leadership.
Bonus credits redeemable on partner tooling.
We re-verify the offer every quarter so it never goes stale.
Hit the button on this page — opens the partner site in a new tab.
Check your investor or accelerator benefits portal for the Stax partner code. Y Combinator, Sequoia, and most Tier 1 VCs have codes available.
Renewals stay at the same rate — verified by us, not the vendor.
| Feature | Stax |
|---|---|
| Free trial | 14 days |
| Cheapest paid plan | $0/mo |
| Annual discount | Up to 25% |
| Refund window | 30 days |
| Setup time | < 1 hour |
| Best for | Founders |
“The right processor for high average ticket businesses”
“Predictable processing costs finally in our budget model”
“Saved $2,400/month switching from Square to Stax”
1 free transaction for new accounts
FREE until your first $1Million in revenue
Free Business Account
Verified offer
$30 signup discount for new users
Verified offer
Free Basic plan + partner onboarding
Free payment terminal + flat 0.99% rate via partner link
