UK Companies House API: free company registry data guide

Every endpoint on this page was live-probed on 2026-07-29 by the Aidenix Atlas catalog.

What is the Companies House API?

The Companies House API is the official free REST interface to the UK company register, covering more than 5 million registered companies, according to Companies House statistics. One API key — issued free on registration — unlocks company profiles, filing history, directors, and beneficial owners. In our data, it is the single richest no-cost company registry in Europe: unlike most EU registers, it exposes ownership, not just existence. The three record types that matter for company research:

• Company profile: legal name, status, incorporation date, registered address, SIC codes.
• Officers: every director and secretary, with appointment dates and other directorships as a join path.
• Persons with significant control (PSC): beneficial owners holding more than 25% — the layer most registries hide.

Key facts at a glance

A key-facts table is the 60-second version of this page: 5M+ companies, one free key, 600 requests per 5 minutes — every row from our own probe run of 2026-07-28, according to the Aidenix Atlas catalog logs:

Which endpoint returns which record?

A Companies House endpoint is a single-purpose route keyed on the company number, and knowing which one holds ownership data saves the usual detour through filing PDFs. Contract checked in our probe run of 2026-07-28:

Which endpoint you need follows from the question, not the API reference order:

• If you are verifying a company exists → the profile endpoint alone, one call.
• If you are doing due diligence → PSC first, officers second; the shell structure shows up in the ownership chain, not the director list.
• If you are batch-processing thousands of companies → the free PSC bulk file, not the API; the rate limit is per key and does not scale.

How do you query the Companies House API?

A Companies House query is a plain HTTP GET with basic auth — the API key goes in the username field and the password stays blank. We tested the endpoints on 2026-07-24; the pattern:

• GET /company/{company_number} returns the company profile.
• GET /company/{company_number}/officers returns directors and secretaries.
• GET /company/{company_number}/persons-with-significant-control returns beneficial owners above the 25% threshold.
• Pass an OE-prefixed number to the same PSC endpoint to read the Register of Overseas Entities — foreign companies holding UK property.

# the trailing colon is not a typo — key goes in the username field, password stays empty
curl -u "YOUR_API_KEY:" \
  "https://api.company-information.service.gov.uk/company/00000006/persons-with-significant-control"

We probed the endpoint without a key on 2026-07-28 and it answered 401 {"error":"Empty Authorization header"} — worth knowing, because that response is how you tell a live endpoint from a dead one when you are testing infrastructure rather than data.

According to Companies House documentation, the rate limit is 600 requests per 5-minute window per key — enough for roughly 172,000 lookups a day. Endpoint, auth, and limits in one table: the Companies House access card.

What makes the PSC register different from other registries?

The PSC register is a beneficial-ownership layer: since 2016, UK law requires companies to declare every person or entity controlling more than 25% of shares or voting rights. Most company registries stop at the legal shell; the PSC register names who actually stands behind it, with nationality, country of residence, and nature of control. In our data, this is the highest-leverage UK dataset for due diligence: chains of shell companies collapse once you follow PSC links two or three hops. Companies House also publishes the full PSC file as a free bulk snapshot — we track it as a separate source for batch workloads, so you crawl the API only for fresh deltas rather than the whole register.

Can you search UK companies by name for free?

Yes — the same API has a search endpoint, and local open-data portals add regional slices. In our catalog, the Camden borough portal alone republishes 801,903 Companies House records filtered to London postcodes, queryable by name, address, and date range without any key. The practical free stack for UK company work:

• Companies House API: profile, officers, PSC — the authoritative record.
• PSC bulk snapshot: full beneficial-ownership file for batch joins.
• HM Land Registry OCOD/CCOD files: which companies own UK property, joinable by company number.

That combination answers UK company-lookup, ownership, and property questions at zero data-license cost — the paid tier only becomes necessary for monitoring at scale. For chains that leave the UK, the GLEIF LEI register supplies the cross-border join key between national registries.

Frequently asked questions

Is the Companies House API really free? Yes — registration takes minutes and there is no paid tier for the standard API. The data is Crown copyright under the UK Open Government Licence, so commercial use is allowed with attribution. The only ceiling is the rate limit.

Does the PSC register show every real owner? No, and the gap is worth naming: the threshold is 25%, so a person holding 20% is invisible, and ownership held through overseas entities resolves only if that entity is itself registered. In our data, PSC answers «who controls this company» far better than any commercial alternative and still cannot promise completeness.

What about company financials? Filed accounts are available through filing history, but small UK companies file abridged accounts on a statutory lag — you get a balance sheet months after year-end, not a live P&L. For funding events and current financials, SEC filings cover US entities better; see the SEC EDGAR guide.

How we verify these claims

Our verification method is a live probe, not a citation chain — the endpoint behavior on this page comes from requests we sent ourselves on 2026-07-28. What the probe run covers, in our data:

• Endpoint liveness: the API answered on probe day, out of the nearly 4,000 sources the Aidenix Atlas catalog tracks.
• Auth behavior: the keyless 401 above is unedited API output, verifying the endpoint responds and the contract has not moved.
• Contract checks: routes and field groups verified against the Companies House published specification.
• Freshness contract: when a source drifts, the probe fleet flags it and this page gets re-verified — the «last probed» date above is that promise.

Source facts from the Aidenix Atlas catalog, probed 2026-07-28. Found an error? The catalog re-probes on every report.