The first version of Stax was born from an indignity familiar to anyone with a good idea and a boss: Suneera Madhani pitched a subscription model for payment processing to the company where she worked, and the room laughed. She had spent years in merchant services, including selling terminals door to door from the trunk of a Volkswagen Beetle. What she saw was an industry that made simple transactions feel deliberately murky. A merchant knew what a sale was worth. Figuring out what the processor took required archaeological work.
Madhani's proposal was to strip out the processor's percentage markup and charge a predictable monthly membership instead. She and her brother, Sal Rehmetullah, started Fattmerchant from their parents' home in Orlando in 2014. The name was a little rude on purpose. It pointed at the fattened fee stack they wanted to puncture.
01 / The wedgeThe fee people could finally explain
Payment pricing is never only one number. Card networks and issuing banks collect interchange. Networks add assessments. A processor adds its own margin and other fees. Stax Pay did not abolish the first two layers; no processor can. Its claim was narrower and more useful: pass direct interchange through without a percentage markup, then charge the merchant a subscription and a small fixed amount per transaction.
Current published pricing starts at $99 a month for businesses processing up to $150,000 a year. The next tier is $139 for $150,000 to $250,000, while $250,000 and above begins at $199. Card-present transactions add eight cents; online or keyed transactions add 15 cents. ACH costs 1 percent, capped at $10. The subscription includes invoicing, links and QR codes, recurring billing, analytics, next-business-day funding, tokenization, fraud tools, and support.
A quick break-even sketch
This is an example, not a quote. Card mix, ticket count, hardware, interchange, and an alternative processor's actual markup change the result.
This is also where the model can fail. A low-volume shop can pay more in subscription charges than it saves in markups. A seasonal merchant may dislike paying through quiet months. A company needing a bare gateway, extensive global acquiring, or an instant self-service setup may prefer Stripe, Square, Adyen, Helcim, Finix, or a traditional interchange-plus provider. Stax works when volume, workflow features, and support are valuable enough to carry the fixed fee.
02 / The expansionA checkout button is not a payment business
By 2020, the larger opportunity was moving inside other companies' software. Stax Connect lets a vertical SaaS platform put payments under its own brand, onboard merchants, and share in transaction revenue. Stax can handle underwriting, compliance, fraud monitoring, risk, API integration, and partner support. Larger platforms can use a PayFac-as-a-Service model for more control. Smaller ones can choose referral or reseller arrangements.
The crucial detail is not the API. Many competitors have a capable API. The hard part arrives after integration, when a software sales team has to persuade existing customers to switch processors. Former CEO Paulette Rowe described partners whose payment attachment remained below 20 percent. Stax responded with Connect Plus, supplying sales, marketing, training, back-book outreach, and support as an extension of the platform. Early adopters, the company said, doubled payment revenue.
“It's not just about providing APIs anymore. It's about being an extension of ISV that starts with white labeling.”Adam Gray, Stax chief transformation officer
Sera shows the pitch in practical terms. The field-service software company needed payments for HVAC, plumbing, electrical, and home-service contractors. Its previous provider put support calls into a general queue. With Stax, Sera launched Sera Payments and reported shorter merchant approval times, more processing volume per merchant, and faster issue resolution. Those are not glamorous metrics. They are exactly the ones that determine whether an embedded product becomes revenue or a dusty menu item.
03 / The stackFive products, one increasingly owned transaction
Stax expanded by buying the jobs adjacent to processing. In 2021 it acquired Fusebill, now Stax Bill, for subscription billing; Payment Depot for another transparent pricing model; and CardX for compliant credit-card surcharging. CardX automates disclosures, recognizes card types, and handles reconciliation. It can move the processing cost to a credit-card customer, but not every buyer will accept the experience, debit cards cannot be surcharged, and laws and card-brand rules matter.
The 2023 acquisition of Atlantic-Pacific Processing Systems was more structural. APPS became the foundation for Stax Processing, the layer intended to bring clearing and settlement under Stax's control. BlockChyp followed in 2024, adding a gateway, retail-payment technology, simplified APIs, and onboarding. In 2025, Stax said the end-to-end system was complete, with direct connections to major U.S. card networks.
Why bother owning so much? A typical payment problem can bounce from an independent sales organization to a gateway, processor, sponsor bank, risk vendor, and network. Every baton pass is another queue and another partial view of the data. Stax argues that a single source can coordinate fraud controls, routing, reporting, and support. Its competitive bet is that a roughly 300-person processor can combine the control of a legacy acquirer with more flexibility for a specific vertical.
04 / The resetThe unicorn moment was not the ending
The headline milestone came in March 2022. Stax raised $245 million from Greater Sum Ventures, HarbourVest Partners, Blue Star Innovation Partners, and PSG at a $1 billion valuation. At the time, it served 22,000 businesses and had processed more than $23 billion. The founders framed the capital as fuel for products, hiring, customer expansion, and international growth.
Then the story changed tone. Madhani and Rehmetullah left in 2023. Paulette Rowe arrived as chief executive and pushed the company toward profitable growth, deeper infrastructure, and vertical software partners. In February 2026, John Cimba succeeded her after the processing build was complete. Stax now says it serves more than 39,000 businesses and platforms and processes more than $23 billion annually. The valuation remains a 2022 financing mark, not a live public-market price, and Stax does not publish audited revenue.
What changed the company's mind was not a single failure. The flat-fee proposition worked. But customers kept revealing a larger mess: disconnected invoices, terminals, recurring bills, risk systems, support teams, and software dashboards. Stax followed that mess. The current company is less a clever merchant account and more a collection of payment capabilities being welded into one system.
05 / The marketToo large for a payments boutique, too small to be a giant
Stax sits in an awkward and potentially productive middle. Stripe and Adyen offer global reach, dense developer ecosystems, and a long catalog of financial products. Square pairs payment acceptance with an accessible hardware and software bundle. Finix, WePay, NMI, and Braintree compete for platforms that want payments inside their own experience. Traditional acquirers bring scale, bank relationships, and decades of operating history. Stax cannot win by pretending those differences do not exist.
Its sharper pitch is aimed at established U.S. and Canadian merchants with enough volume to benefit from subscription economics, and at vertical software companies that want to keep their own brand on the payment experience. Those platforms may care less about having every country on a map than about enrolling a plumbing contractor quickly, reconciling six locations, handling healthcare workflows, or getting a named person on a support problem. Stax sells expertise around merchant underwriting, PCI compliance, fraud controls, surcharging, recurring revenue, payment adoption, and the unlovely details of settlement.
That human layer also shapes the culture Stax advertises. Its roughly 300 employees are called the Stax Pack; the company lists integrity, winning together, customer obsession, and ownership of outcomes as operating values. It reports 15 Best Places to Work awards. Culture claims are easy to print and hard to audit, but here the language matches the commercial strategy: a mid-sized processor has to make responsiveness feel like a product, because it will not outspend the largest networks.
06 / The copyable partStart with one hated fee. Follow the friction.
There is a useful playbook here, even for companies that never touch a card number. Stax did not begin by promising to rebuild global finance. It challenged one fee customers already resented, priced the alternative so a buyer could do the math, and used that wedge to earn permission to solve neighboring problems. When software partners struggled to sell payments, Stax treated distribution as product work.
Name the markup, show the monthly fee, and let a customer calculate a break-even point.
An integration without onboarding, seller training, incentives, and support is unfinished.
Stax's acquisitions map to billing, surcharging, gateway, onboarding, processing, and settlement.
Fixed fees reward steady volume. They are less persuasive when usage is light, seasonal, or highly global.
The conditions for failure are equally instructive. Owning the stack creates integration risk, regulatory responsibility, and operating complexity. A software platform without enough merchant volume may never recover its implementation cost. A merchant that values instant signup over human support may find Stax's sales-led process heavy. And no pricing model rescues poor service when money goes missing. Stax's promise rests on execution at the exact moment a transaction becomes urgent.
That is the tension inside Stax now. Transparency made the company legible. Acquisitions made it capable. The next test is whether those pieces feel like one product to the merchant who only wants Friday's deposits to match Thursday's sales. Payment infrastructure is invisible when it works. Stax has spent a decade trying to make the bill - and the people behind it - easier to see.