AI Fintech Funding Alert

US AI Fintech Startup Flex Raises $60M To Redefine Finance For Mid-Sized Businesses

• ByStartupStory     |    December 5, 2025

Series B Led By Portage Ventures Hits $500M Valuation Amid AI Agent Expansion

San Francisco-based AI fintech Flex has raised $60 million in an oversubscribed Series B funding round led by Portage Ventures, pushing its valuation to approximately $500 million and bringing total equity raised to $105 million. The capital accelerates development of an AI-native “private bank” for profitable mid-sized businesses—those generating $2-100 million in annual revenue—offering integrated private credit, payments, business cards, cash forecasting, and personal finance tools.

AI Agents Replace Manual Back-Office Work

Flex targets “jumbo shrimps”—mid-market firms comprising 40% of U.S. payroll but underserved by enterprise fintech and traditional banks lacking dedicated finance teams. CEO Zaid Rahman positions Flex as the complete financial stack: “We serve a few hundred thousand business owners with AI agents handling credit underwriting, expense management, payments, cash flow, and ERP integration.”

Key innovations:

• Credit agents: Real-time underwriting with human verification to minimize errors

• Expense/payment agents: Automated workflows tripling payment volume to $3B in past year

• Flex Elite card: Upcoming consumer card rivaling Amex Centurion for high-net-worth owners

Financial professionals oversee AI outputs, addressing MIT studies showing only 5% of AI pilots scale.

Capital Fuels Product Roadmap And Hiring

Proceeds expand AI agent infrastructure, product innovation, and team growth from 80 to support broader client acquisition. Rahman emphasized focus: “Extensive products for specific clientele bridging enterprise sophistication with mid-market accessibility.”

Existing backers Sequoia, Lightspeed, and Greenoaks reaffirm conviction in Flex’s execution amid AI fintech surge.

$100B+ TAM In Underserved Mid-Market

Mid-sized firms face fragmented tools—manual spreadsheets, slow banks, limited credit—while generating massive economic value. Flex unifies via single platform, enabling cross-border credit, AI CFO tools, and generational wealth transfer.

Competitors target SMBs/consumers; Flex carves premium mid-market niche. Payment volume growth signals traction.

Challenges: AI accuracy, regulatory compliance. Strengths: human-AI hybrid, rapid scaling.

Flex’s $60M validates AI redefining B2B finance—agents as virtual CFOs unlocking efficiency for overlooked engines of U.S. economy.

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