To check whether a UK company is in administration, search for it by name or company number on administrator.uk. Each company page shows its current status and the filings behind it. The underlying official sources are Companies House, where the appointment is filed as form AM01, and The Gazette, the UK's official public record of insolvency notices.
Type the company's name or its eight-digit company number into the box above. The company's page shows its current status (active, in administration, in liquidation, or dissolved) alongside its registered address, directors, and filing history. If it's in administration, you'll see when the administrators were appointed and which firm they're from.
This is the fastest check because it pulls the relevant public records into one place, so you don't have to cross-reference Companies House and The Gazette yourself.
If you want to go to the primary sources, there are two:
Three things tell you what you need to know: the status itself (is it administration, or actually liquidation or a winding-up petition: they're different things); the date of appointment, which tells you how far into the process the company is; and the administrator's firm, which is who you'd contact if you're a creditor. If you're owed money, the creditor checklist is the next stop.
Confirmed is the free tier. Add up to five companies, and you get an email the day one of them goes into administration. No card, no trial. Protect adds the earlier warning signs, well before it's official, across an unlimited number of companies.