API
Build anything on top of Truster
Invoicing without the manual work
Truster's partner API takes the manual work out of invoicing: you set up your workers once under your own identifier, and from then on a single batch carries up to 5,000 lines — work, compensation, per diems, mileage and receipt-backed expenses in one submission, for hundreds of workers at a time. In Finland, a processed batch becomes one consolidated invoice.
One bad line never sinks the batch: every line gets its own outcome (accepted, quarantined or rejected), and a quarantined line is fixed and resent under the same identifier. Retries are safe — an idempotency key replays the original response, and the same line can never be invoiced twice.
The documentation is public: interactive API docs (api.truster.com/api/v2/docs), a machine-readable OpenAPI document and an integration guide (api.truster.com/api/v2/guide), all readable without signing in. The guide is written so you can hand it to your AI and ask for the integration.
Up and running in a day, not weeks
- 01
Request an API key
Our customer service issues your key — sk_test_… for the sandbox; your production key (sk_live_…) comes when we open production for you. The key also sets your market (Finland or Sweden), and GET /settings tells you right away what it may do.
- 02
Open the docs
The API docs and the integration guide are public: api.truster.com/api/v2/docs and /api/v2/guide. No sign-in, no NDA.
- 03
Let your AI integrate
Give your AI (Claude, Cursor, Copilot…) the address of the integration guide or the OpenAPI document and ask it to connect your system to Truster — the guide is written for exactly that.
- 04
Test in the sandbox
Build and test with an sk_test_ key in the sandbox before anything is invoiced for real. When everything works, we open production.
The documentation is open
Browse the API in the interactive docs or read the integration guide — both without signing in.
Batches and lines
Up to 5,000 lines per batch. Add, edit, move and delete lines by your own externalRowId — no Truster-internal id is ever needed.
Workers
Set up a worker with their national identity number, or with the worker's own share code so you never handle identity numbers at all.
Per diems and mileage
Per diems, mileage and — in Finland — meal allowances are priced at the tax authority's official rates. The rates and VAT treatments come straight from the API.
Receipts
Attach a receipt to an expense line: AI reads the merchant, date, totals and VAT and checks them against the amount you declared.
Consolidated invoice
In Finland, a processed batch becomes one consolidated invoice, readable from the API.
Webhooks
Receipt processing and worker status changes arrive as webhooks, so there is no polling for receipts. You read batch and invoice status from the API.
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.
- Lines per batch
- 5,000
- Line types
- Work · compensation · allowance · purchase
- Markets
- Finland · Sweden
- Sandbox
- sk_test_ keys
Verified on 25 September 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.