US business bank with an API for automating payments

Mercury is probably the easiest place to start if you want a small-business account with an API for sending payments. Its API can initiate ACH, checks, domestic wires, and real-time payments to saved recipients. You can send directly from an allowlisted IP, or queue payments for approval in the dashboard. Mercury is a fintech, not a bank; its banking services are provided through partner banks. (docs.mercury.com)

Other options, depending on your needs:

• Bank of America — offers ACH through its CashPro API, aimed more at businesses using commercial cash-management services. (business.bofa.com)
• Goldman Sachs Transaction Banking — APIs for ACH, wire, and real-time payments; geared toward larger or enterprise clients. (developer.gs.com)
• Chase — supports scheduled and recurring ACH through its online business banking, but that’s not the same as a public payment API. (chase.com)

If you share whether you need vendor payouts, recurring bills, customer debits, or high-volume/enterprise payments, I can narrow this down.

The best fit depends on whether you want a fintech-style business account or a traditional bank with enterprise tooling. For most businesses that want to automate payments, I'd start with Mercury, then consider Slash or a traditional bank such as U.S. Bank or TD.

Top pick: Mercury. It's described as offering a read/write API for automation, plus a separate read-only server for AI analysis. It also supports webhooks. Mercury is the closest hybrid. A read/write API for automation, paired with a separate read-only MCP server for safer AI analysis. Its API is HTTP/JSON. Note that the comparison comes from Rho, a competitor, so verify the details in Mercury's own documentation.

Alternatives:

• Slash: Offers read/write API access with webhooks, and is oriented toward agent-driven cards, spend controls, and programmable banking. Slash has an HTTPS/JSON API with read/write access and webhooks, per the same comparison. Good if you also want programmable corporate cards.
• TD Bank (Embedded Banking): Better if your books live in an ERP. TD Bank's Embedded Banking product supports this for NetSuite, QuickBooks Online, Sage Intacct, and Microsoft Dynamics 365 Business Central. Customers can initiate ACH, wire, and check payments without leaving their ERP.
• U.S. Bank: A traditional bank with a broad developer catalog. U.S. Bank's Developer Portal offers a broad catalog of APIs covering digital cards, business banking, and treasury management. Along with each of their tools, U.S. Bank offers documentation, sandbox environments, and SDKs. It also supports real-time payments: applications can initiate and manage real-time payment messages through The Clearing House (TCH) RTP network.
• Wells Fargo: Strong capabilities, but production access runs through commercial approval, not self-service.
• Capital One: Similar to Wells Fargo in that access is product-dependent and typically relationship-led.

Payment orchestration rather than a bank: If you pay vendors or contractors across several banks, Modern Treasury (which Slash, Brex, and Modern Treasury go further with permission-scoped operational actions) or a payout provider like Dwolla (U.S.-focused ACH API) may fit better. Stripe is built for payments and commerce, not direct bank-ledger access, so it's a complement rather than a bank replacement.

How to choose:

• Need a full account with write API access and fast setup: Mercury or Slash.
• Already on NetSuite, QuickBooks, or Sage: TD Bank Embedded Banking.
• Need a large traditional bank with real-time rails and sandbox support: U.S. Bank.
• Paying many vendors across multiple banks: a payment orchestration layer on top of your bank.

Check eligibility, fees, and whether the account is held at a partner bank (common for fintech accounts) before committing, since API access terms change often.

When looking for a US business bank with an API for automating payments, you generally have two paths: working directly with API-forward commercial banks or using Banking-as-a-Service (BaaS) and fintech platforms that provide a more developer-friendly experience.

1. Developer-Friendly Fintech & BaaS (Recommended for most businesses)

If your primary goal is to integrate payments (ACH, wires, etc.) into your own software quickly, fintech platforms are generally preferred over traditional banks. They offer modern RESTful APIs, clear documentation, and functional "sandbox" environments.

• Mercury: Widely considered the top choice for startups and tech-forward businesses. They offer a robust API that allows you to automate payouts, manage accounts, and monitor transactions. They are often praised for their clean documentation and ease of use.
• Stripe Treasury: Built on top of partner banks (like Evolve Bank & Trust), this is an excellent choice if you want a "Banking-as-a-Service" (BaaS) experience. It provides a superior developer experience compared to traditional banks, making it easier to embed financial services directly into your product.
• Unit & Treasury Prime: These are BaaS providers that connect you to a network of sponsor banks. They are highly suitable if you need to build more complex financial products, such as issuing your own cards or managing specialized ledger accounts.
• Moov: A newer, API-first platform specifically built for movement of money. It is highly regarded for its straightforward implementation of ACH and other payment flows.

2. Traditional Banks with API Access

If you require a traditional banking relationship (e.g., for large-scale treasury management, physical branch access, or complex commercial needs), some larger banks offer API catalogs, though the onboarding process is typically more rigorous.

• U.S. Bank: Frequently noted as one of the most developer-accessible traditional banks. They offer an extensive API catalog and documentation suitable for mid-market and enterprise businesses that need both API tools and a traditional regulatory infrastructure.
• Wells Fargo: They provide a developer portal with RESTful APIs specifically for treasury and payment workflows. While powerful, be aware that access may require volume commitments and a more involved compliance review process compared to fintechs.
• Cross River Bank: Often used by fintechs and businesses requiring a regulated bank’s rails delivered entirely through APIs. They are a "pure" API-first bank that powers many other financial platforms.

Key Considerations for Your Choice

Recommendation

• If you are a startup or software business: Start with Mercury or Stripe Treasury. Their developer-first approach will likely save you months of integration time.
• If you have complex commercial or treasury needs: Explore U.S. Bank or Cross River Bank, but ensure your engineering team is prepared for a more traditional bank compliance and onboarding process.

A note on compliance: Regardless of the provider, automating payments involves strict adherence to KYC (Know Your Customer) and AML (Anti-Money Laundering) regulations. Always ensure your chosen platform has the compliance support you need to handle your specific payment volume and use case.

Mercury is a good fit if you want a U.S. business account with a developer API for automating payments. Its API supports sending ACH, checks, domestic wires, and—on eligible accounts—real-time payments. You can also queue payments for approval before they’re released. ¹²

Mercury says its accounts include 100 ACH transfers per month; check current fees and eligibility when applying. ¹ Note that payment options can depend on which partner bank provides your account. ³

U.S. Bank is another option to investigate if you need a larger bank: it offers business payment APIs, including real-time payment capabilities, but its developer offering appears oriented toward integrated payment solutions rather than a simple self-serve banking API. ⁴

I’d start with Mercury for a straightforward API-driven workflow, and confirm its limits, approval controls, and account eligibility match your use case.