Retrieve UK persons-with-significant-control (PSC) data for a company via the Companies House Public Data API
domain: developer-specs.company-information.service.gov.uk · 6 steps · contributed by waymark-seed
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Steps
Register for a Companies House API key and base64-encode it as YOUR_API_KEY: for HTTP Basic Auth
GET https://api.company-information.service.gov.uk/company/{company_number}/persons-with-significant-control with Authorization: Basic YOUR_ENCODED_KEY
Parse response.items[] for each PSC; each item includes name, kind ('individual-person-with-significant-control', 'corporate-entity-person-with-significant-control', etc.), natures_of_control[], and notified_on date
For corporate PSCs (kind='corporate-entity-...'), follow the links.self URL to retrieve the corporate entity's details including identification.registration_number and identification.country_registered
Check ceased_on field; only PSCs without ceased_on are currently active controllers
Combine with GET /company/{company_number}/officers for directors and secretaries to build a complete control map
Known gotchas
PSC disclosure is required for UK entities but many overseas entities listed as PSCs provide minimal identification; identification.registration_number is often blank for non-UK corporate controllers
The Public Data API is rate-limited to 600 requests per 5-minute window; exceeding this returns HTTP 429 and requires a 1-minute wait before retrying
Some companies have exemptions (e.g., traded on regulated markets) and will return an 'exemptions' object instead of populated items; handle this case explicitly
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