Sign inBook a demo

API

Build anything on top of Truster

Invoicing without manual work

Truster's B2B API removes all the fiddling from creating invoices: add your workers once, and after that an entire invoice batch is generated with a single call — even for a hundred workers at once, expense reimbursements and mileage included. The API validates tax cards straight from the source, returns finished PDFs, and webhooks confirm events back to your system. Retries are safe thanks to idempotency keys — a network outage never produces a duplicate invoice.

The documentation is public: the interactive Swagger docs (api.truster.com/api/v1/docs) and the integration guide (api.truster.com/api/v1/guide) can be read without logging in. The guide is written in machine-readable markdown — hand it to your favorite AI and ask it to build the integration, and you're set. Truster's core also speaks the Connect protocol (JSON, gRPC and gRPC-web from the same endpoints), if you're building something deeper.

Up and running in a day, not weeks

  1. 01

    Request an API key

    Get your API keys from our customer service. The key is authenticated with a Bearer header, and /auth/verify instantly tells you which company it's linked to.

  2. 02

    Open the documentation

    The Swagger docs and integration guide are public: api.truster.com/api/v1/docs and /guide. No login, no NDA required.

  3. 03

    Let AI do the integration

    Give your AI (Claude, Cursor, Copilot…) the integration guide's address and ask it to connect your system to Truster — the guide is written so that the AI can do the integration for you.

  4. 04

    Test in Mock Mode

    Our sandbox validates calls and requires a real key, but writes nothing to production. Once everything works, we switch production on.

The documentation is open

Browse the API in Swagger or read the integration guide — both without logging in.

API documentationIntegration guide

Invoices and batches

Create a single invoice or an entire batch with one call — and fetch the finished PDFs directly from the API.

Workers

Add workers with personal details, a distribution code or Business ID (Y-tunnus) — using your own externalKey identifier.

Webhooks

Events are pushed to your own system the moment an invoice goes out or a payment arrives.

Tax cards and enforcement records

An up-to-date tax card is checked directly from OmaVero (the Finnish Tax Administration's online service) before invoicing.

One call, a finished invoice

The API responds with JSON — and a webhook carries the event into your system.

Illustration: an API call creates an invoice — the request is sent, the server responds with 200 OK, and a webhook delivers the event to your own system.

API services
68
Protocols
Connect · gRPC · JSON
Sandbox
Mock Mode
Accounting exports
Netvisor · Fortnox · Procountor · Visma

Verified on 22 July 2026

Your first integration in days

Request an API key from customer service or book a demo, and we'll walk through the API for your use case.

Book a demoFor AI: MCP