Companies House

Companies House

UK government register of companies. Search and retrieve company data including profiles, officers, filing history, and charges. No account or API key is required from the user — the platform supplies access.

Questions you must refuse

• "Which company has the most charges / filings / debt in the UK?" — there is no national ranking endpoint. Do not search several retailers and compare total_count. Tell the user the API only supports named company lookups and ask which companies they want.

Operational order

1. Search by company name or keyword → take company_number from a result (8 characters, often zero-padded, e.g. 00445790, SC123456).
2. Profile with the company profile lookup using that company_number.
3. Officers or filing history or charges with the same company_number when the task needs people, filings, or secured charges.

Do not guess a company number from memory. Always search first when you only have a trading name.

Data model

• Company search — paginated hits with company_number, title, company_status, date_of_creation, registered address snippet.
• Company profile — registered office, SIC codes, accounts and confirmation-statement due dates, status, type.
• Officers — directors, secretaries, LLP members; appointment and resignation dates, roles.
• Filing history — chronological filings (accounts, confirmation statements, appointments). Large histories: use category filter and small items_per_page before paging with start_index.
• Charges — mortgages, debentures, and other registered charges.

Gotchas

• Company numbers: Eight characters, zero-padded where needed. Scottish companies use SC prefix; Northern Irish use NI.
• Rate limits: The upstream application quota is 600 requests per 5 minutes (shared platform key). Prefer targeted calls and pagination over repeated full-history fetches.
• Pagination: start_index (0-based) and items_per_page. Filing history can return thousands of rows — filter by category when possible.
• Not found: Unknown company_number returns a not-found error; re-run search if the number may be wrong.

Honesty contracts (no fabrication)

• No cross-company rankings: The API exposes per-company search and detail endpoints only. There is no popularity, charge-count leaderboard, indebtedness ranking, or "most filings" index across all UK companies. Do not compare a hand-picked sample of retailers (or any subset) and declare a winner. Say the API cannot rank companies globally and offer to look up specific company names the user names.
• Filing history is not one-shot complete: total_count on a filing-history response is the register total for that company, not proof you retrieved every filing in this call. Large companies (e.g. Tesco) have thousands of filings. Do not claim "complete" or "every filing ever" from one page or from total_count alone. Use category (e.g. accounts) and small items_per_page, page with start_index only when the user needs more rows, and state how many items this call actually returned versus total_count.
• Charges counts are per company: total_count on charges is for that company_number only. Comparing charges across companies requires explicit per-company lookups, not a single search.