This version is in beta - expect some breaking changes.

Self Assessment Individual Details (MTD) API

Available in Sandbox Yes
Sandbox base URL
Available in Production No


This API allows developers to perform operations related to Individuals/Taxable Entities for Income Tax Self Assessment:

  • Retrieve ITSA status for a given NINO for a specified tax year and optionally for future years

For information on how to connect to this API see the Income Tax MTD end-to-end service guide .


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.

Single errors will be returned in the following format:
{     "code": "FORMAT_FIELD_NAME",     "message": "The provided FieldName is invalid" }

Where possible, multiple errors will be returned with INVALID_REQUEST in the following format:
{     "code": "INVALID_REQUEST",     "message": "Invalid request",     "errors": [         {      "code": "RULE_FIELD_NAME",      "message": "The provided FieldName is not allowed"         },         {      "code": "FORMAT_FIELD_NAME",      "message": "The provided FieldName is invalid"         }     ] }

Where it is possible for the same error to be returned multiple times, message will describe the expected format and paths will show the fields which are invalid.

Where arrays are submitted a number indicates the object in the array sequence, for example, /arrayName/1/fieldName

An example with single error:
{     "code": "FORMAT_STRING_NAME",     "message": "The provided field is not valid",     "paths": [ "/arrayName/0/fieldName" ] }

An example with multiple errors: {     "code": "INVALID_REQUEST",     "message": "Invalid request",     "errors": [      {      "code": "FORMAT_VALUE",      "message": "The value should be between 0 and 99999999999.99",      "paths": [ "/objectName/fieldName1", "/arrayName/0/fieldName2" ]      },      {      "code": "FORMAT_STRING_NAME",      "message": "The provided field is not valid",      "paths": [ "/arrayName/0/fieldName3", "/arrayName/1/fieldName3" ]      }     ] }


You can use the sandbox environment to test this API. You can use the Create Test User API or it's frontend service to create test users.

It may not be possible to test all scenarios in the sandbox. You can test some scenarios by passing the Gov-Test-Scenario header. Documentation for each endpoint includes a Test data section, which explains the scenarios that you can simulate using the Gov-Test-Scenario header.

If you have a specific testing need that is not supported in the sandbox, contact our support team.

Some APIs may be marked [test only]. This means that they are not available for use in production and may change.


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.


View API endpoints
Why 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.