Format verdict
Whether the number has the right length and letter series for a UK company number.
Free tool
UK Companies House Number Check
Type an eight-character Companies House number and get an instant format verdict: plain digits or a known two-letter series plus six digits, with leading zeros preserved.
- Free to try
- No API key
- Live register data
Free checkerNo key needed
The result appears here. Nothing is stored, and the allowance is per visitor per day.
Example result
A plain eight-digit number
- Company number
- 00445790
- Format
- Eight digits
- Leading zeros
- Kept
- Verdict
- Well formed
The check judges the format alone. Use UK company search or a profile call to confirm the company behind the number.
A real check above replaces this example.
What you get
Normalized number
The eight-character form with leading zeros kept, ready to paste into search or an API call.
Series detected
Plain eight digits, or a known prefix such as SC or NI when the number uses a letter series.
FAQ
Common questions
Does this search Companies House?
No. It checks the format of the number in your browser. To search the register, use UK company search on this site or pass the number to GET /v1/companies/gb/{company_number} after you have a key.
Does a valid number prove the company exists?
No. A valid format only means the number is well formed. It does not prove the number was issued or that the company is still trading.
Why does 4457900 not work?
A UK company number is eight characters wide, so the leading zeros count. 00445790 is a valid shape and 4457900 is not.
What are the two-letter prefixes?
SC is Scotland, NI is Northern Ireland, OC is a limited liability partnership, and other series cover society, overseas and similar registers.
Is the check free?
Yes. No account is needed. The format rule runs in your browser first, so a typo is free to correct, and a well-formed company number uses one of the tool's 5 daily checks.
Is a company number the same as a VAT number?
No. A company number identifies the legal entity in the register that issued it. A VAT number is issued by a tax authority and has its own check on this site.