Once you’ve completed your company formation, it’s vital that you use an effective filing system to stay organised as you’ll be dealing with a plethora of documents and important identification numbers — nominally your company tax number and company number. Since there’s little to differentiate these numbers textually, it’s important to recognise and understand that both your company tax number and company number areseparate numbers.

To give you a better understanding of these all-important numbers, let’s look at both your company and company tax numbers’ definitions and uses:

What Is a Company Tax Number?

Often referred to as a “tax reference number”, UTR is an acronym for “Unique Taxpayer Reference”.  Your company tax number (UTR number) comprises 10 digits (e.g. 0123456789) and is issued by HMRC to all UK residents who complete a tax self-assessment, such as a self-employed individual, sole trader, or limited company owner.

For those who work in the construction industry, an application for both a company tax number and a Construction Industry Scheme registration (CIS registration) must be made.

A company UTR number (company tax number) is used to identify companies for issues related to tax. The company tax number will be required for a number of reasons, such as tax submissions to HMRC and the following:

  • When you change your corporation tax accounting period
  • To contact HMRC for company-related issues
  • For VAT returns and tax filing
  • To inform HMRC about changes to your registered details or company structure
  • To inform HMRC if your company is dormant
  • Payment of corporation tax and VAT
  • To pay your employees
  • To register for corporation tax, VAT, and PAYE

How Do You Find Your Existing Company Tax Number?

In case you’ve forgotten your company tax number, there are a number of ways to retrieve these all-important digits.

Most of your HMRC correspondence will show your company tax number; make sure you check your tax returns letters or documents such as a P60 or P45. Your company tax number will also be printed on your payslip.

See this list for where your company tax number may be located:

  • Your company’s online Corporation Tax account
  • Your online Self Assessment account
  • The “Welcome to Self Assessment” letter sent by HMRC
  • The “Corporation Tax Information for New Companies” letter sent by HMRC
  • The informative letter containing your Self Assessment activation code
  • Notices to file a Corporation Tax return or Self Assessment tax return
  • Account statements
  • Payment reminders
  • Previous Corporation Tax or Self Assessment returns
  • Any similar official letters/notices sent by HMRC

If you still can’t access previous tax documents (or you simply want to check your company tax number) you can call the self-assessment helpline or follow the detailed HMRC instructions here.

Note: If you’re an overseas tax payer, you may need to make an international payment to HMRC (this may be expensive because of high international banking fees). Remember, traditional banks can charge you an administration fee to process the international payment, therefore we advise you to refer to your individual bank policies.

What Is a Company Number?

Simply put, a company registration number is an identifiable registration number for your company.  It will be issued to you by Companies House when you incorporate your limited company or limited liability partnership (LLP). A company registration number is often abbreviated as “CRN” and is computer generated, therefore it cannot be personally selected or amended at a later date.

Unlike a company tax number, your company number will either have eight numbers (e.g. 12345678) or two letters followed by six numbers (e.g. AB123456). However, unlike a company tax number, a company registration number can take a number of visual forms depending on where you incorporate your company and the type of company you choose to set up. See this guide for more details about a company registration number without the need to run a Companies House search.

How Do You Find Your Existing Company Number?

Your company’s Certificate of Incorporation, along with any statutory mail sent by Companies House, will display your company registration number. The company registration number is usually printed alongside or beneath a heading such as “Company No.” You may also find it on the public register next to your company details.

Additionally, it is a legal requirement to display your limited company’s registration number on all your business stationary. This includes, but not limited to, the following:

  • Letterheads
  • Faxes
  • Compliment slips
  • Emails
  • Invoices
  • Receipts
  • Online content
  • Order forms

Note: There may be a number of occasions when you’ll have to use your company registration number. For example:

  • Communicating with Companies House
  • Submitting annual returns
  • Filing your accounts
  • Changing your company name
  • Changing your registered office/SAIL address
  • Adding a new company director/secretary
  • Removing an existing company director/secretary
  • Changing the details of directors and secretaries
  • Registering for business taxes
  • Paying your Corporation Tax
  • Filing Company Tax Returns
  • Filing copies of resolutions
  • Increasing capital of shares
  • Issuing share certificates.
  • Issuing dividend vouchers
  • Amending your Accounting Reference Rate (ARD)


It’s vital that you familiarise yourself with your all-important company numbers to prevent, for example, any confusion with your company number and your company tax number.

Staying organised is crucial for a smooth workflow as you may come across other numbers in addition to your company tax number and company number, leaving an unorganised CEO rather overwhelmed. For example, your VAT number and Employment Numbers both differ from each other as well as differing from your company number and company tax number.

A VAT number is issued by HMRC for companies registered for Value Added Tax and contains nine digits, with the “GB” prefix (e.g. GB123456789), while your Employer reference number is issued by HMRC when employers register to implement PAYE (Pay as You Earn) for their employees. The first part of the reference consists of three digits, identifying the tax office that deals with the appropriate PAYE. The second part follows a forward slash, and identifies the tax office’s employer reference (e.g. 123/AB456). 

If you’re a business owner seeking more information about both your company registration number, and company number, contact our dedicated company formations team now for expert assistance.