What is a UK company number and what do the prefixes mean?

What is a company number?

A company number, also called a company registration number or CRN, is the identifier Companies House allocates to a company when it is registered. Section 1066 of the Companies Act 2006 requires the registrar to give every company a registered number, in any form of figures or letters the registrar decides. The number stays the same when the company changes its name or moves its registered office, which makes it the safest way to identify a company.

The format

Every company number has 8 characters:

• England and Wales companies: 8 digits, with leading zeros. TESCO PLC is 00445790.
• Everything else: a 2-letter prefix and 6 digits, for example SC followed by six digits for a Scottish company.

People often drop the leading zeros, so 445790 and 00445790 refer to the same company. Search tools and APIs expect the full 8 characters, so pad a purely numeric number with zeros on the left. A small number of older registered society and LLP numbers also contain letters at the end.

Prefixes and what they mean

The prefix tells you which register and which part of the UK the entity belongs to. All of the prefixes below appear in the Companies House register file, except where noted.

An HMRC reference list for Corporation Tax records, last updated in 2012, covers the older prefixes and notes that Scottish and Northern Ireland limited partnership numbers (SL, NL) are not set up for Corporation Tax. The prefix is part of the number: SC123456 and 123456 are different companies.

How many companies are there?

The Companies House register file of 1 October 2026 held 5,704,712 companies, LLPs and other entities of all live statuses, and the large majority have plain 8-digit England and Wales numbers. Dissolved companies keep their numbers but drop out of the monthly file. See the status values for what each status means, and UK companies by accounts type for how those companies file.

Where to find a company's number

A company must show its registered number, the part of the UK where it is registered and its registered office address on its business letters, order forms and website. That rule is in regulation 25 of the Company, Limited Liability Partnership and Business (Names and Trading Disclosures) Regulations 2015. You will usually find the number in a website footer, on an invoice or in an email signature.

If you only have a name, search the Companies House register or our company search, and check that the registered office matches the address on the invoice.

Validating a company number in code

A simple check that catches most typing errors:

function normaliseCompanyNumber(input) {
  let n = input.trim().toUpperCase().replace(/\s+/g, "");
  if (/^\d{1,8}$/.test(n)) return n.padStart(8, "0");
  const m = n.match(/^([A-Z]{2})(\d{1,6})$/);
  if (m) return m[1] + m[2].padStart(6, "0");
  return /^[A-Z0-9]{8}$/.test(n) ? n : null;
}

normaliseCompanyNumber("445790");   // "00445790"
normaliseCompanyNumber("sc 12345"); // "SC012345"

The last line accepts the rare 8-character numbers with letters in other positions. A number that passes this check can still belong to no company: the only real test is a lookup against the register, such as the /v1/company call in our API quickstart.

Sources

• Companies Act 2006, section 1066
• The Company, Limited Liability Partnership and Business (Names and Trading Disclosures) Regulations 2015, regulation 25
• HMRC: Company registration number formats
• Companies House API enumerations (GitHub)

FAQ

How many digits is a UK company number?

Eight characters. Companies registered in England and Wales have eight digits, often starting with zeros, such as 00445790. Companies in Scotland, Northern Ireland and other entity types such as LLPs and overseas entities have a two-letter prefix followed by six digits, such as SC, NI, OC or OE plus six numbers.

Is the company number the same as the VAT number or UTR?

No. The company number is issued by Companies House and identifies the company on the public register. The VAT registration number and the Unique Taxpayer Reference (UTR) are issued by HMRC for tax purposes and follow different formats. A company's UTR is not public, while its company number must appear on its letters, order forms and website.

What does OC mean in a company number?

OC marks a limited liability partnership (LLP) registered in England and Wales. Scottish LLPs use SO and Northern Ireland LLPs use NC. LLPs file accounts and confirmation statements at Companies House like companies, but they have members instead of directors and shareholders.

What does OE mean in a company number?

OE marks an overseas entity on the Register of Overseas Entities, which Companies House keeps for foreign companies and other legal entities that own or buy land and property in the UK. It is different from FC, which is an overseas company that has registered a UK establishment, such as a branch, to do business here.

Sources: Companies House register and accounts data (Open Government Licence v3.0), legislation.gov.uk and GOV.UK guidance where linked. This page is general information, not legal, tax or credit advice. Spotted an error? Email info@globalmindsetmarketing.co.uk.