Stax
Subscription-style processing with 0% markup on interchange.
What is Stax?
Stax (formerly Fattmerchant) is a payment processing platform that charges a flat monthly subscription with 0% markup on interchange, instead of per-transaction percentage markups. It targets established businesses with higher processing volumes.
Best known for: Subscription pricing with 0% markup on interchange
Key features
- Subscription-based pricing
- 0% interchange markup
- In-person and online payments
- Invoicing and recurring billing
- Payment analytics dashboard
- Developer API via Stax Connect
Who Stax is best for
- Higher-volume merchants who save with a flat monthly membership
- Businesses processing well above ~$10K/mo in card volume
- Owners who want wholesale interchange with no percentage markup
Ideal team: Established SMBs with steady, higher card volume who come out ahead trading a monthly fee for zero interchange markup.
Stax pricing
Membership (to $150K/yr)
$99/flat / mo + per-txn fee
- 0% markup over interchange
- 8¢ in-person / 15¢ online per transaction
- For up to $150K annual processing
Membership ($150K–$250K/yr)
$139/flat / mo + per-txn fee
- Same 0% interchange markup
- Same 8¢ / 15¢ per-transaction fees
- For $150K–$250K annual processing
Membership ($250K+/yr)
$199/flat / mo + per-txn fee
- Starts at $199/mo for high volume
- 0% interchange markup retained
- For $250K+ annual processing
Costs to watch before you commit
- At low volume the monthly membership erodes savings — break-even is roughly $8K–$10K/mo in card sales.
- You still pay the underlying interchange on top of the membership + per-transaction fee.
- Optional modules (e.g. advanced reporting, terminals) can add to the base membership.
Top Stax alternatives
Popular Payments & POS tools teams evaluate alongside Stax.
SquareAll-in-one POS, hardware, and payments for retail, food, and services.
Checkout.comEnterprise payment orchestration with interchange++ and multi-acquirer routing.
GoCardlessBank debit and ACH collection built for recurring and invoice payments.
Lemon SqueezyMerchant of record for digital products, SaaS, and subscriptions.
Authorize.netLong-standing payment gateway that plugs into existing merchant accounts.