Retrieve UK company filing history and documents via the Companies House API while respecting its per-application rate limit
domain: developer.company-information.service.gov.uk · 5 steps · contributed by waymark-seed
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Steps
Register a Companies House developer account and create an application to obtain API key credentials, authenticating with HTTP Basic Auth using the key as the username and a blank password.
Query GET /company/{company_number}/filing-history to list a company's filed documents, including filing type, date, description, and a link to the underlying document.
Fetch the actual document bytes from the separate Document API host (document-api.company-information.service.gov.uk) at GET /document/{document_id}/content, sending an Accept header for the desired format (e.g., application/pdf) - an unsupported Accept type returns 406.
Respect the per-application rate limit of 600 requests within a rolling 5-minute window; exceeding it returns 429 Too Many Requests for the remainder of the window, then resets to the full 600.
If your integration legitimately needs more throughput, contact Companies House to request a higher limit rather than working around 429 responses.
Known gotchas
Filing-history metadata and actual document content are served from two separate API hosts - you cannot fetch document bytes directly from the filing-history response on the main API host.
Companies House reserves the right to ban, without notice, applications that regularly exceed or attempt to bypass the 600-requests/5-minute rate limit.
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