Banking as a Service API

Embedded GBP & EUR banking

One API to onboard clients, open accounts, send payments, and receive real-time notifications across your entire portfolio. Go from sandbox to live in days, not months.

Get started → API reference →

REST + HTTPS JSON payloads HMAC-SHA256 auth GBP + EUR Faster Payments SEPA Credit Transfer 26 webhook events Sandbox environment FCA-authorised EMI

Getting started

Set up credentials, sign your first request, and make your first API call against the sandbox.

Authentication

Step-by-step HMAC-SHA256 signing with examples in Python, Node.js, Java, C#, and C++.

API reference

Complete documentation for all 22 REST endpoints with request and response schemas.

Why Mercury

Multi-currency

GBP + EUR from one API

Single integration for sterling and euro. No juggling separate providers or parallel integrations.

Speed

Seconds, not days

GBP Faster Payments settle in seconds. SEPA Credit Transfers same-day. API responses in milliseconds.

Real-time

26 webhook events

Instant notifications for every client, account, and payment event. No polling required.

Verification

Built-in Confirmation of Payee

Verify beneficiary names before sending payments. Reduce fraud and misdirected transfers.

Regulated

FCA-authorised EMI

Client funds safeguarded. Mercury handles regulatory complexity so you can focus on your product.

Developer-first

Modern REST API

Clean RESTful design, HMAC signing, comprehensive error responses, and detailed webhook payloads.

First API call in 4 steps

Get credentials

Receive your API Key and Secret Key from the Mercury team.

Request access →

Sign your request

Generate an HMAC-SHA256 signature from your API key, method, path, body, and nonce.

Guide →

Call the sandbox

Hit GET /api/v1/client against the sandbox environment.

Walkthrough →

Explore and build

Browse the API reference, explore architecture patterns, and start building.

API reference →

API capabilities

Clients

Onboard and manage end-clients. Full lifecycle from creation through KYB to closure.

GBP accounts

Open sterling accounts with dedicated sort codes and account numbers. Query balances and statements.

EUR virtual IBANs

Create euro virtual IBANs with SEPA connectivity. Full account management and statement retrieval.

GBP payments

Send and receive GBP via Faster Payments. Real-time settlement notifications via webhooks.

EUR payments

Initiate SEPA Credit Transfers across Europe. Track payment status through to settlement.

Confirmation of Payee

Verify beneficiary account details before payment. Reduce fraud and misdirected transfers.

Webhooks

Real-time notifications for 26 events across clients, accounts, and payments.

Lookup data

Currencies, countries, business types, risk ratings, and CoP reference data.

Sterling payments

Create and manage GBP payment transactions with full status tracking.

Integration guides

Architecture patterns → Client onboarding → GBP account management → EUR virtual IBAN management → Multi-currency operations → Error handling → Webhooks → Postman collection → Code examples (5 languages) → Authentication helper tool →

Ready to integrate?

Tell us about your integration and the Mercury team will be in touch to set up your sandbox access.

Request API access → Contact the team →

200Returns the client

400Reference not found or client is not Active — "Client with the provided reference could not be found or their account is not Active"

500Internal server error