San Francisco fintech quadruples revenue serving business owners generating $3M-$100M annually, a segment employing 40% of American workers.
While big banks court billionaires and fintechs chase small businesses, a massive segment of wealthy Americans has been left without modern financial tools. Flex is changing that, and investors are paying attention.
The company announced today it has closed a $60 million Series B funding round led by Portage, with participation from CrossLink Capital, Spice Expedition, Titanium Ventures, Wellington, and others. The raise brings Flex’s total equity funding to $105 million and follows a year of explosive growth that saw the company quadruple revenue and triple its payments volume to $3 billion.
The $3 Million to $100 Million Gap
Flex targets what founder and CEO Zaid Rahman calls the “forgotten middle”, business owners generating between $3 million and $100 million in annual revenue. These entrepreneurs collectively employ roughly 40% of America’s workforce, yet they’ve been forced to juggle more than ten disconnected financial systems to manage their money.
“Middle-market business owners employ 40% of Americans, but the financial system has never been designed around their complex needs,” Rahman said. “Unlike many of our FinTech peers who focus on saving large enterprises money, we focus on helping ambitious owners make more money.”
AI Agents Running Your Back Office
What sets Flex apart is its aggressive bet on artificial intelligence. The company is deploying AI agents across every aspect of its platform, from credit underwriting that deeply analyzes each business to expense management, payment workflows, and cash management systems that work together like a “motherboard” for business owners.
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The vision is ambitious: give every business owner a team of high-quality finance agents that run their back office like an enterprise operation. Flex calls this its “AI CFO” approach, transforming customer data into intuitive insights while maintaining a lean internal headcount.
Taking on American Express Centurion
Timing the announcement strategically, Flex is launching Flex Elite today, an invite-only premium card and membership designed as a direct competitor to the legendary American Express Centurion (Black Card). The move signals Flex’s expansion from business tools into high-end personal finance, creating what Rahman describes as a true “private bank” for the middle market.
The company’s Business Credit Card, which offers a 60-day float on every transaction, has proven to be the gateway product. Once owners experience the benefits, they typically adopt Flex’s banking, payments, working capital, and expense management tools, replacing their fragmented legacy systems. Customers now use an average of four or more Flex products.
The Private Credit Advantage
Supporting everything is Flex’s private credit arm, which uses its AI-powered underwriting system to price risk with greater precision than traditional banks. This vertically integrated capital engine creates what the company calls a “defensibility loop” — more lending volume leads to more product adoption, which generates better data, improving risk models and unit economics.
After raising $200 million in debt and $25 million in equity earlier this year, this $60 million Series B positions Flex as one of the fastest-growing fintech companies in America, distinguished by what investors call “best-in-class capital efficiency.”
“Flex is building a category-defining financial institution,” said Jake Bodanis, Partner at Portage. “The company has proven that middle-market business owners are both massively underserved and extremely valuable customers when given the right financial infrastructure.”
Building the Complete Financial Stack
Flex’s five-pillar strategy encompasses private credit, business finance tools, personal finance products, payment solutions, and an ERP system built specifically for middle-market businesses. The goal is to capture the complete lifecycle of money for this segment, from the moment they earn revenue in their business to the moment they spend it personally.
With personal finance products for affluent individuals largely unchanged for decades, Flex sees an opportunity to bridge business and personal finances in a way that reflects how wealthy business owners actually operate. The company’s long-term ambition is to become the central platform this segment relies on to grow and transfer wealth across generations.
For America’s middle-market business owners, that integration can’t come soon enough.
