For developers

The Claims API is a REST API with a published OpenAPI contract and a Sandbox.

The Sandbox

Every registered organisation has a Sandbox twin, where claims are checked as HMRC would check them and nothing reaches HMRC. Your Sandbox key arrives when your organisation is approved, alongside the live one.

The contract

• A key is a bearer token, sent with every request; the organisation comes from the key, never the request.
• A claim is filed at most once, whatever your retries do.
• Totals are computed by the API, exact to the penny.
• Every refusal has a name and says why.