Guides for developers and data teams
Plain-English guides to UK company rules and checks: what a company's status means, what it has to file and when, and what to check before you trade with it, lend to it or take it on as a client.
- Companies House API alternatives compared (2026)Comparison
If you only need register records, the free Companies House API, its streaming API and its bulk files are hard to beat. Alternatives earn their price by adding something: figures parsed from accounts, credit scores and CCJs, other countries or more volume. OpenCorporates covers 140+ jurisdictions, Endole and Creditsafe add credit data, and CompanyStack adds parsed accounts.
- Companies House API rate limits explainedGuide
The Companies House REST API allows up to 600 requests within a five-minute period for each application, an average of two a second. Over that, every further request in the same period gets HTTP 429 Too Many Requests until the limit resets. You can ask Companies House for a higher limit, and it can ban applications that keep exceeding it.
- Companies House bulk data products explainedGuide
Companies House publishes three free bulk downloads: a monthly CSV snapshot of every live company (the Free Company Data Product), daily and monthly files of electronically filed accounts in iXBRL and XBRL (the Accounts Data Product, archived back to 2008), and a daily JSON snapshot of people with significant control. Officer data is not offered as a free download.
- How to get UK company financial data through an APIHow-to
The Companies House REST API does not return financial figures: the company profile gives only accounts dates and the accounts type. The figures are in the filed accounts. Fetch them through the Document API (iXBRL for electronic filings, PDF for paper), download the free Accounts Data Product in bulk, or use an API that has already parsed them.
- How to parse UK iXBRL company accounts in PythonHow-to
Install ixbrlparse (version 0.11.2 tested here), open the file with IXBRL.open, then pick each figure by its FRC concept name, its period (the balance sheet date, or the year ending on it) and its dimensions (none, for totals). Skip nil facts, which the library reads as zero, and check scale and sign on anything that looks odd.
- Using an MCP server for UK company dataHow-to
An MCP server lets an assistant such as Claude Code, Claude Desktop or Cursor call company data tools itself. For UK company data you can connect a hosted server such as CompanyStack's by its URL, with an API key in an X-Api-Key header, or run an open-source server that wraps the Companies House API with your own key.
- How to check whether a director or PSC has verified their identityHow-to
Search the company on the Companies House register and open the People tab. Each director shows either 'Verification requirements complete' or 'Identity verification due' with a date, and each PSC shows a 'due from' and 'due by' window. Status is recorded per appointment, so check each company separately; the Companies House API returns the same dates.
CompanyStack for developers and data teams
What the web app and the API do for you, on which plan, with real samples.