UK company number format checker.

How a UK company number is built

A company number is the identifier Companies House gives each entity on its register, and HMRC publishes its own note on the same formats. Two government documents describe the shape. HMRC's "Company Registration Number Formats" note says England and Wales companies have registration numbers that consist of 8 digits, and that Scottish and Northern Irish companies, and those registered through the financial regulator, carry a one- or two-character alphabetic prefix. The Companies House customer guide to its URI scheme gives the prefix list in full and shows the layout with two examples: 02050399 and SC002180. This checker applies those rules. Type a number and it tells you whether the shape fits, which prefix it carries, what the prefix means and which jurisdiction it points to.

The prefix list

The table merges the Companies House list with HMRC's. A "Yes" in the HMRC column means HMRC's note lists the same prefix. Five prefixes (SE, ES, EN, NC and NV) appear only in the Companies House guide. The last column reflects a statement in the Companies House guide: for the IP, SP, IC, SI, NP, NV, RC, SR, NR and NO prefixes it holds nothing but the company name and number.

Worked example

Take the Companies House guide's own examples. 02050399 is 8 digits with no letters, so it passes as an England and Wales company with no prefix. SC002180 is the prefix SC followed by six digits, so it passes as a Scottish company. Now a hypothetical mistake: NI12345 has the NI prefix but only five digits after it, so the tool rejects it and explains that a two-letter prefix is followed by 6 digits. And 2050399 has only seven digits, so the tool suggests 02050399, because the official layout keeps the leading zero.

Common mistakes and edge cases

• Lost leading zeros. A number copied through a spreadsheet or cast as an integer can lose its leading zero. England and Wales numbers are shown with all 8 digits.
• Lower case or spaces. The guide writes prefixes in upper case. The tool uppercases and strips spaces so that sc 002180 still resolves.
• OC and SO. The two documents describe these differently. The Companies House guide lists OC and SO as limited liability partnerships for England and Wales and for Scotland. HMRC's note says its OC and SO codes are used only for LLP cases in liquidation. The tool shows the Companies House meaning and prints the HMRC caveat.
• The R prefix. HMRC lists a single-letter R for Northern Ireland companies registered before the 1922 partition; the Companies House guide writes it R0. The tool accepts R0 followed by six digits and says so.
• Prefixed length. Neither document states the length of prefixed numbers outright. The tool expects a two-letter prefix plus six digits because the Companies House guide's own example, SC002180, is eight characters.
• Age of the documents. The Companies House guide is version 1.1 from May 2012 and the HMRC note was saved in February 2012. A prefix introduced later will not be in either list, and the tool reports it as "Prefix not in the lists" instead of calling the number wrong, with a link to the register.

Who this is for

Bookkeepers and onboarding teams who want to catch a malformed number before a supplier or KYC form is submitted, developers who need to know what shapes a company number can take, and anyone who has been handed a code like NC or SL and wants to know what kind of entity it points to.

What this does not cover

The checker does not query the register, so it cannot tell you whether a company exists, is dissolved or is dormant. A well-formed number can still be unallocated. It does not validate VAT, UTR or PAYE references, which are different identifiers. For a real result, use the link the tool provides to the official Companies House page for the number, or the existing Companies House lookup page on this site.

Sources

• Companies House: Uniform Resource Identifiers (URI) Customer Guide, v1.1 (05/12), "List of Company Numbers and Prefixes"
• HMRC: Company Registration Number Formats (2012)
• Companies House: Find and update company information (the live register)

Retrieved 20 October 2026. Issuing bodies can change these rules; check the source if a result matters.

FAQ

How many digits is a UK company number?

HMRC says England and Wales company numbers consist of 8 digits, and leading zeros are kept (for example 02050399). Companies with a letter prefix, such as SC002180, are also 8 characters in all.

What does the SC prefix on a company number mean?

SC stands for a Scottish company in the Companies House guide. The number is SC followed by six digits.

What does the NI prefix on a company number mean?

The Companies House guide lists NI as a Northern Ireland company (post-partition). R0 marks a Northern Ireland company registered before the partition of Ireland in 1922.

What do the OC and SO prefixes mean?

Companies House lists OC as a limited liability partnership for England and Wales and SO as one for Scotland. HMRC’s note says its OC and SO codes are used only for LLP cases in liquidation.

Do UK company numbers have leading zeros?

Yes. England and Wales numbers are 8 digits, and the Companies House guide’s example is 02050399. A number that shows only 7 digits has usually lost its first zero in a spreadsheet.

Which prefixes does Companies House hold only a name and number for?

The Companies House guide says it holds only the company name and number for IP, SP, IC, SI, NP, NV, RC, SR, NR and NO. These cover industrial and provident societies, investment companies with variable capital, royal charter companies and Northern Ireland credit unions.

Can I tell if a company is active from its number?

No. The number only reflects layout, jurisdiction and entity type. Whether the company is active, dormant or dissolved is shown on the register, which this tool links to.

Does this tool check VAT, UTR or PAYE numbers?

No. Those are different identifiers with their own formats. It covers company registration numbers only.