Companies House publishes a free snapshot of every live UK company once a month: name, number, status, incorporation date, up to four SIC codes, registered office post town and postcode, and the accounts and confirmation statement due dates. If you sell to new businesses, or just want to know who started up in your sector and area last month, that file is all you need.

This post does it twice: first with pandas on the raw file, then with a hosted API that keeps the monthly comparison for you. At the end there's a due-date check for a list of client companies, the free API way and the hosted way.

Disclosure: the hosted API in the second half is ours, and it's paid per row. The free route comes first and works without it.

The free route: the Basic Company Data file

Download it from the Free Company Data Product page . It's split into 7 zipped CSV files of about 70 MB each (the 1 October 2026 snapshot has 5,704,711 live companies).…