How to find a UK company's registration number

A company's registration number is the one reliable way to identify it. Names change, trading names differ from legal names, and several companies can have almost the same name. The number never changes. If you want to check a customer, watch it for warning signs, or file a claim, you need the right number. This guide shows where to find it and how to match a whole list of customers at once.

What the number looks like

Companies House gives every company a registration number, also called a company number or CRN. HMRC's manual describes it as up to eight numerals, or normally two letters (a prefix) followed by up to six characters.

In practice:

• Companies registered in England and Wales usually have eight digits, for example 00445790 (Tesco PLC).
• Companies registered in Scotland start with SC, for example SC011620.
• Companies registered in Northern Ireland start with NI, for example NI019095.
• Limited liability partnerships (LLPs) have their own prefixes, such as OC for LLPs registered in England and Wales.

Numbers are often written without their leading zeros, so 445790 and 00445790 are the same company. Our tools accept either.

Where to find it

1. On the company's own paperwork and website. The law requires a UK company to 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 websites (regulation 25 of the Company, Limited Liability Partnership and Business (Names and Trading Disclosures) Regulations 2015). Look at the bottom of an invoice, a quote, an email signature or the company's website footer.

2. On the Companies House register. Search by name at find-and-update.company-information.service.gov.uk. The number is shown under each result. Check the registered office address and status too, so you pick the right company when several have similar names.

3. In your accounting software. Some systems have a field for it. Xero contacts, for example, have a company registration number field, but it is often left empty.

Watch out for:

• Trading names. "Smith's Bakery" may be the trading name of "J Smith Holdings Limited". Use the legal name on the invoice or website footer.
• Groups. Big brands often have many companies with similar names, such as a group company and an operating company. Make sure you pick the one you actually trade with, usually the name on your contract or invoices.
• Sole traders and partnerships. These are not companies, so they are not on the Companies House register and have no company number.

Matching a whole customer list

Looking up hundreds of customers one by one takes a long time. FilingPing can do it for you. On your account page, upload a list of company names, for example a customer export from Xero, QuickBooks or Sage. FilingPing looks each name up on the Companies House register and suggests the match. When exactly one active company has that name, it is selected for you. Anything uncertain is left for you to choose or skip, and nothing is added until you confirm.

Once you have the numbers, the free bulk company check shows the warning signs for up to 20 companies at once. FilingPing can then watch them and alert you when anything changes.

Sources

• HMRC Company Taxation Manual, COM40011: company registration numbers (gov.uk).
• The Company, Limited Liability Partnership and Business (Names and Trading Disclosures) Regulations 2015, regulation 25 (legislation.gov.uk).
• Example numbers and prefixes taken from the Companies House register, 1 October 2026.

Updated 1 October 2026 · All guides