Mercury vs Brex vs Relay: Best Business Bank Account for Startups
Your business bank account is not just where money sits — it is the foundation of your financial stack. Mercury, Brex Cash, and Relay are the three fintech options that consistently win with startups, and they make meaningfully different trade-offs on yield, team controls, and integration depth.
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The Quick Answer
Mercury is the default recommendation for most startups: clean UI, no fees, strong API, and it just works. Relay is better if you run a team with complex payment workflows and need multiple checking accounts with granular permission controls. Brex Cash makes sense if you are already on the Brex card ecosystem and want unified spend management in one dashboard.
Side-by-Side Breakdown
Mercury: No monthly fees. No minimum balance. FDIC insured up to $5M through partner banks. Treasury product earns yield on idle cash. Strong API for fintech founders. ACH, wires, and check support.
Relay: No monthly fees (Relay Pro at $30/month adds perks). Up to 20 checking accounts and 50 debit cards per business. Strong team permission controls. Built for businesses with multiple revenue streams or departments.
Brex Cash: Free with Brex card. FDIC insured up to $6M. High-yield on operating balance. Tightly integrated with Brex expense management. No standalone checking account without the card product.
When to Choose Mercury
You are a startup, LLC, or solo founder who wants a clean, no-fee business account that works on day one. You need a solid API for custom integrations or financial automation. You want one account to hold operating cash plus a Treasury option for idle funds. Mercury is also the easiest to open — most applicants get approved within 24-48 hours without a branch visit.
When to Choose Relay
You run a team with multiple people making payments and you need role-based controls. You want to allocate money into separate accounts by category — payroll, taxes, operating expenses, owner's pay — and track each bucket separately. Relay's multi-account structure is the closest a fintech gets to Profit First banking methodology in practice.
When to Choose Brex Cash
You are already using Brex for your corporate card and want a single platform for spend management, reimbursements, and cash. You want yield on your operating balance without moving money to a separate Treasury account. You want to see card spend and bank balance on the same dashboard.
The Verdict
Start with Mercury unless you have a specific reason not to. It has the broadest startup ecosystem support, the cleanest UI, and no gotchas. Upgrade to Relay if you find yourself wishing for account segmentation or team payment controls. Add Brex Cash if you go all-in on the Brex card ecosystem.
How to Get Started
Mercury: Apply at mercury.com with your EIN, business formation documents, and personal ID. Approval is typically same-day to 48 hours.
Relay: Apply at relayfi.com. Plan your account structure before you open — deciding how many sub-accounts you want up front saves a reorganization later.
Brex Cash: Open through the Brex onboarding flow when you apply for the card. You cannot open Brex Cash as a standalone product without the card.
RECOMMENDED TOOLS
Mercury
No-fee startup banking with API access
Relay
Multi-account business banking for teams
Brex
Banking + corporate cards in one platform
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FREQUENTLY ASKED QUESTIONS
Are Mercury and Relay real banks?
No. Both are financial technology companies that partner with FDIC-insured banks to hold deposits. Your deposits are FDIC insured, but Mercury and Relay themselves are not chartered banks.
Can I use Mercury or Relay for payroll?
Yes — both support ACH transfers needed for payroll. But most businesses use a dedicated payroll platform (Gusto, Rippling, ADP) and simply connect it to their Mercury or Relay account for the ACH pull.
Which account earns the most interest on cash?
Mercury Treasury earns a competitive yield on balances over $500K. For smaller balances, Brex Cash currently offers the highest yield on operating balances among the three. Rates change frequently, so compare current rates at account opening.