Company UTR vs personal UTR: which one goes on the CT600?

Use your company’s 10-digit Corporation Tax UTR for its CT600. Your personal Self Assessment UTR belongs to your own tax record, even if you are the company’s only director and shareholder.

HMRC asks for the company’s UTR when you add Corporation Tax services to its business tax account. See the company registration guidance.

Why it is easy to pick the wrong number

A UTR is a Unique Taxpayer Reference. Both an individual registered for Self Assessment and a limited company can have one, and both references contain ten digits. Counting digits alone will not tell you which record the number belongs to. HMRC explains the different UTR records.

Think of a director preparing two returns: the company’s CT600 and their own Self Assessment return. The company reference belongs with the company return; the personal reference belongs with the personal return. Being responsible for both does not make the references interchangeable.

Where to find the company’s UTR

Look at the company’s previous tax returns and HMRC correspondence, such as a notice to file or a payment reminder. Check that the document names your company.

If you cannot locate it, use the online Corporation Tax UTR request linked from HMRC’s UTR guidance. HMRC sends the reference to the business address registered with Companies House, so check that you can receive post there.

Your own Personal Tax Account or HMRC app can show your individual UTR. Do not assume that a number found there is the reference for your limited company.

Keep the company number separate

The company registration number and the Corporation Tax UTR are separate identifiers. HMRC lists both when explaining how to add Corporation Tax services. If a form asks for the UTR, use the ten-digit tax reference; keep the company number for the field that asks for it. HMRC’s list of required details.

A quick check before continuing

Before entering the reference, check three things:

• The source document relates to the correct company.
• You have selected its Corporation Tax reference.
• The number has been copied completely, including any leading zero.

If you are unsure, confirm the reference with HMRC before submitting. Do not guess from a similar-looking number or use a personal reference to get past a required field.

Have your company details and year-end figures ready? Start your CT600 with filefast.

Checked on 1 October 2026.

Matvei Kostiuchenko, Founder of filefast. Not an accountant. This article is general information, not a substitute for regulated tax advice.