The UK Government Gateway HMRC Individual Tax API retrieves an individual's tax information (tax record) for a given year. The primary intended use for this information is to pre-populate an individual's Self Assessment tax return. The API is available in JSON formats with Token as the authentication method. With the API, developers can integrate tax deductions from gross income, pensions, and benefits. A Sandbox base URL is available at: https://test-api.service.hmrc.gov.uk/
The current version of 1.1 is still in beta and the 1.0 version is depreciated at this time.
HMRC is responsible for the administration and collection of taxes in the UK.