“Can a flat-rate SMB payment processor evolve into the full financial operating system for small businesses and ISVs by stacking lending, billing, and embedded payments on top of its payment rails?”
Founded in 2014 as Fattmerchant with a disruptive flat-rate/interchange-plus subscription model for SMB payment processing, the company rebranded to Stax in 2021 and expanded from pure payment processing into a full integrated payments platform. Stax layered on embedded payments for ISVs (Stax Connect), billing/invoicing (Stax Bill with Avalara tax automation), and SMB lending (Stax Lending/Capital), positioning itself as an all-in-one financial OS for SMBs and software platforms. The original sibling founders exited circa 2023–2024 as the company crossed $1.1B valuation; new leadership is executing a go-to-market and technology realignment in 2026.
Stax processes payments through Stax Payments (self-operated) and Stax Connect (self-operated).
Stax's lending and capital products are provided by Lendflow.
The Embedded Finance Index 2026 maps 2 layers in Stax's stack: Payments / PSP (Stax Payments (self-operated) and Stax Connect (self-operated)); Lending (Lendflow, Term Loan (6–36 months, up to $10M), Receivables Advance (3–12 months, up to $750K) and Line of Credit (revolving, up to $10M)).
Stax was founded by Suneera Madhani and Sal Rehmetullah and is founded in 2014, headquartered in Orlando, FL, United States.
Stax has raised $245M in total (latest round: Series D (Debt most recent per PitchBook); valuation: $1.1B+ (at founders' exit)).
Get a read on where your own stack stands against Stax and the rest of its category — what they built versus bought, which providers they use, and where the gaps in your own strategy and competitive set actually are.