Check a UK company by API: Companies House

Companies House · read from the national register · checked 11 November 2026

The official route

Companies House has a free REST API. You register on the developer hub, create a key and send it as the HTTP Basic user name. The limit is 600 requests per 5 minutes per key, and going over it returns 429 for the rest of that window. The company profile gives the name, status, type and registered office. Other endpoints list officers, persons with significant control (PSCs) and charges. The data is Crown copyright under the Open Government Licence v3.0. Companies House also publishes free daily ZIP files of electronically filed accounts, and those need no key.

Where it gets hard

Insolvency sits in two places. A winding-up petition is advertised in The Gazette before the hearing, and Companies House does not show a pending petition.
The Gazette's full-text search misses most company numbers. We ended up matching on the exact registered name, which loses notices under a former name.
The Gazette's fair use policy (read 2026-11-07) allows automated tools 5 requests every 10 seconds and asks for crawling between 9pm and 7am UK time.
About 75% of accounts are filed electronically (iXBRL). The rest are paper or PDF with no data to read. Most small companies file accounts without a profit and loss account, so you get balance-sheet figures only.

One call

{"query": "Tesco PLC", "country": "GB"}

Post that body to https://api.boscolabs.dev/v1/counterparty-check. A name can fit several companies. The company number (00445790 for Tesco) always resolves exactly.

Check	Source for this country
Register status	Companies House
Insolvency	Companies House insolvency cases and The Gazette (our nightly copy of corporate notices since 2020)
People on sanctions lists	Directors and PSCs from Companies House
Recent accounts	Companies House digital accounts; listed companies also ESEF reports
Company on sanctions lists	OFAC, UN, UK, EU and US export lists
LEI status	GLEIF
IBAN	ISO 13616 check digits; no bank is contacted

$0.05 per company checked, empty and failed calls are free.

What we do not cover

VAT numbers: VIES does not cover GB numbers, only Northern Ireland (XI).
Gazette notices from before 2020, notices published today (the copy is made at night) and notices under a former name are not found.
Paper and PDF accounts give no figures.
Personal insolvency notices are never kept, and officers' addresses are never output.

Sources

Get a key: $5.00 free, no card Try the planner without a key

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