This version is in beta - expect some breaking changes.

Individual Losses (MTD) API

Dates and amounts
Date Amount
Version and status
Available in Sandbox Yes
Sandbox base URL
Available in Production No


This API allows developers to provide financial data for Brought Forward Losses and Loss Claims.

For Brought Forward losses a developer can:

  • provide a list of brought forward losses
  • create a new brought forward loss
  • show a single brought forward loss
  • update an existing brought forward loss
  • delete an existing brought forward loss

For Loss claims a developer can:

  • provide a list of loss claims
  • create a loss claim against an income source for a specific tax year
  • show the detail of an existing loss claim
  • update a previously entered loss claim
  • delete an existing loss claim

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:

"message": "The provided FieldName is invalid"


Where possible, multiple errors will be returned with INVALID_REQUEST in the following format:

"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"



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.

Fraud Prevention

HMRC monitors transactions to help protect your customers' confidential data from criminals and fraudsters.

Warning You are required by law to submit header data for this API. This includes all associated APIs and endpoints.

Check the data you need to send. You can also use the Test API during initial development and as part of your quality assurance checks.


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.


The way we show Individual Losses (MTD) API v4.0 endpoints has changed, which might look different to other Developer Hub APIs.

The API has not changed. You do not need to make any updates to your application if you already use this API.