Self Assessment Assist (MTD) API
| Available in Sandbox | Yes |
|---|---|
| Sandbox base URL | https://test-api.service.hmrc.gov.uk |
| Available in Production | No |
Overview
The HMRC Assist report is generated using the customers’ National Insurance number (NINO), Calculation ID and Tax year. The report contains targeted messages contained within the JSON response for the customer.
This API allows developers to:
- retrieve a HMRC Assist report for a given customer with a list of messages for the customer
- securely generate a report that is sent to or displayed after it has been generated
- allow the client to acknowledge the report
Errors
We use standard HTTP status codes to show whether an API request succeeded or not. They are usually in the range:
- 200 to 299 if it succeeded, including code 202 if it was accepted by an API that needs to wait for further action
- 400 to 499 if it failed because of a client error by your application
- 500 to 599 if it failed because of an error on our server
Errors specific to each API are shown in the Endpoints section, under Response. See our reference guide for more on errors.
Testing
You can use the HMRC Developer Sandbox to test the API. The Sandbox is an enhanced testing service that functions as a simulator of HMRC’s production environment.
Versioning
When an API changes in a way that is backwards-incompatible, we increase the version number of the API. See our reference guide for more on versioning.
Endpoints
View API endpointsWhy do these endpoints look different?
The endpoints for this API now use the Open API Specification (OAS).
The API has not changed. You do not need to make any updates to your application if you already use this API.