The middle-market founder doesn’t see themselves as a banker. Yet many of them run financial systems more tangled than a Wall Street trading desk. Ten platforms for payments. Another handful for expenses. A spreadsheet maze for both business and personal life.
As Zaid Rahman (pictured below) started talking to these owners, he kept hearing versions of the same line: No one has ever built a system for people like us.
That gap has now turned into one of the fastest-growing fintech stories in the country.
Flex, the Miami-born startup positioning itself as an AI-native private bank for high-net-worth business owners, announced today that it has raised a fresh $60 million in Series B funding. The round, which was led by Portage and included Florida Funders, brings total equity raised to $105 million. The funding lands after a year in which Flex quadrupled revenue and pushed its annualized payments volume from $1 billion to $3 billion, according to the company’s announcement.
For most early customers, the big shift was the idea that someone finally understood the strange space they occupy. Traditional fintech tends to chase micro-businesses or Fortune-500-scale enterprises.
Flex focuses on the band in the middle: profitable companies with $3 million to $100 million in revenue, a group Rahman described as the financial backbone of the country.
“Middle-market business owners employ 40% of Americans, but the financial system has never been designed around their complex needs,” he said in a statement.
That mismatch between responsibility and support is exactly what Flex is trying to fix. Its approach looks less like a bank and more like an operating system. Owners start with something simple – often the Flex Business Credit Card, which gives 60-day float on every purchase – and then expand into banking, payments, working capital, and expense tools. Part of the appeal is consolidation: once owners move onto Flex, they no longer juggle the patchwork of software they’ve stitched together over the years.
But the real story is the AI architecture running behind the scenes. Flex is building a suite of AI agents across its product pillars, designed to handle tasks that usually bog down a company’s back office. The company describes these as underwriting agents, cash-flow agents, expense agents, ERP agents – all feeding into a central system that behaves like a digital finance team.
Flex framed its vision simply: to give every customer “a team of high quality finance agents to run their backoffice like an enterprise,” and then translate the resulting data into what it calls AI-powered Owner Insights, effectively handing each customer an “AI CFO.”
It’s an ambitious plan, but investors seem convinced the middle market is ready for it. “Flex is building a category-defining financial institution,” commented Jake Bodanis of Portage, the lead investor.
Bodanis continued: “The company has proven that middle-market business owners are both massively underserved and extremely valuable customers when given the right financial infrastructure. Flex’s hypergrowth and best in class capital efficiency speaks to how powerful this model is.”
Flex’s capital model is a core part of that pitch. The company operates its own private credit arm, supported by an “agentic underwriting system” that it says allows more precise pricing of risk. The more Flex lends, the smarter the underwriting engine becomes. That loop – data in, risk models out – is what Rahman believes will help the company scale with stronger margins while expanding the number of financial products each customer adopts.
And now Flex is stretching into an area where banks have barely changed anything in decades: personal finance for the wealthy. Its new invite-only consumer card, Flex Elite, debuts this week as a direct challenge to Amex Centurion. The move connects the dots between the business owner’s company balance sheet and their personal life, which tend to be intertwined in ways that traditional institutions rarely accommodate.
“Flex is the first platform that supports every step of their financial lives, from the moment they earn revenue to the moment they spend it personally,” Rahman said.
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