Partner Filing API

Overview

This reference describes a release-gated API for approved Practice integrations. Live access is not generally available. A test key uses an isolated sandbox. Read API access and filing responsibilities before integrating.

The endpoint selects the destination. POST /filings/ct600 sends HMRC returns and POST /filings/accounts handles Companies House accounts. To file both, make two operations with separate idempotency keys and check both results. The form's filing_target remains the shared draft and browser-resume choice.

Documentation

• Getting started: Get a test key, prepare a complete request, review a dry run and poll CT600 and company accounts filings through the Partner Filing API.
• Testing: Test keys, sandbox companies and captured requests for acceptance, rejection, authentication failure and mixed outcomes across two CT600 returns.
• Dates and dry runs: Accounts dates, Corporation Tax coverage, two-return accounting periods, customer-entered allocations and both figure-entry modes in API dry runs.
• Outcomes and retries: Read each filing part, download documents, handle authority reasons and use idempotency keys and retry_of for explicit resubmission.
• Errors: Every Partner Filing API error code, message and HTTP status with links to the endpoints that return it, generated from the contract.
• Endpoints: Every Partner Filing API endpoint with described parameters, typed response fields, status-specific errors and captured request and response examples from the generated contract.
• Filing fields: Shared filing request fields, types, help and constraints generated from the plain-form contract and the same field help used by the wizard.
• Examples: Complete fictional API request examples for company, club and charity routes, long accounting periods, amendments and individual filing choices.
• Versioning and changelog: The current API version, release status, version policy, exclusions and dated release notes read from the reviewed contract metadata.

Endpoints

Download the generated contract

• OpenAPI YAML
• OpenAPI JSON
• TypeScript request and response types
• Small TypeScript client