Company UTR vs personal UTR: find the right one for a CT600

By Max Szolcek, founder of Dormant Return. Last updated 17 September 2026

A Company Tax Return needs the company's Corporation Tax Unique Taxpayer Reference. The trouble is that a director usually has a second UTR of their own for Self Assessment, and both are 10-digit numbers from HMRC that look exactly alike. Enter the wrong one and HMRC does not say "wrong UTR": it says it could not sign you in. Here is how to tell the two apart, where to find the company's, and what to check when a filing is refused.

What the company UTR is

HMRC gives every company registered for Corporation Tax a 10-digit Unique Taxpayer Reference. gov.uk describes it as the number that "will be on all letters from HMRC and HMRC online services". It identifies the company's Corporation Tax record: filing software sends it inside the return, and HMRC checks it against its records before accepting anything. A UTR your Government Gateway sign-in is not set up for is refused at sign-in, before the return is read (error 1046, below); a UTR HMRC cannot find at all is rejected with error 1608.

Four numbers get mixed up with it:

The company registration number from Companies House. Eight characters, public, printed on the certificate of incorporation. This is not the UTR, though a Company Tax Return needs both.
Your personal UTR for Self Assessment. Also 10 digits, also from HMRC, and belonging to you rather than to the company. A common mistake is to enter it in the company's return; see what happens if you use the wrong UTR.
The Corporation Tax payment reference, the 17-character reference you use when paying HMRC for an accounting period. It is on the notice to deliver a return and on HMRC reminders, next to the UTR, but it is a different number and is not what a return asks for.
The Government Gateway user ID, which is a sign-in credential of up to 12 characters, not a tax reference at all.

Company UTR or personal UTR: how to tell

Both are 10 digits and nothing in the number itself says which kind it is. What tells them apart is where the number came from:

It is the company's UTR if it came from a letter addressed to the company at its registered office (the letter after incorporation, a CT603 notice to deliver a Company Tax Return, a Corporation Tax reminder or penalty), or if it is shown against Corporation Tax in the company's business tax account.
It is a personal UTR if it came from your own Self Assessment: a letter addressed to you at home, a Self Assessment tax return or statement, your Personal Tax Account or the HMRC app. gov.uk lists those as the places to find an individual UTR.
It may be another company's UTR if you are a director of more than one company, or run a company that took over from an earlier one. Each company has its own UTR, so check the company name on the letter as well as the number.

If you are not sure, the company's business tax account settles it: sign in with the Government Gateway user ID you will file with, open Corporation Tax, and use the UTR shown there.

What happens if you use the wrong UTR

Filing software sends the UTR alongside your Government Gateway sign-in, and HMRC checks that the sign-in is set up for Corporation Tax on that exact UTR before it reads anything else. If it is not, because the UTR is a personal one, belongs to another company or has a digit wrong, HMRC refuses the sign-in with error 1046: "Authentication Failure. The supplied user credentials failed validation for the requested service."

That message looks like a wrong password, so the natural reaction is to check the password, confirm it works on gov.uk, and try again, which gets the same error. We tested this against HMRC's own test service on 17 September 2026: correct sign-in details with a UTR the account was not set up for gave error 1046 every time, and filing with the right UTR was accepted straight away. The same week, a customer of ours who was certain of their password had entered a different UTR; changing it was all it took to file.

So if HMRC says it could not sign you in but the same user ID and password work in the business tax account, compare the UTR on the return with the one shown against Corporation Tax there before trying again. On Dormant Return you do not need to start over or pay again: after a refused sign-in, the filing page shows the UTR on the return and lets you change it, then checks the return again before you file. The other causes of error 1046 are covered in CT600 rejected by HMRC: what the error codes mean.

Where it appears

Look for a 10-digit number, sometimes printed with a space after the fifth digit, on any of these:

The letter HMRC posted after incorporation. When a company is registered at Companies House it is usually set up for Corporation Tax at the same time, and HMRC posts the UTR to the registered office address. gov.uk says it should arrive within 15 working days of registration.
The CT603 notice to deliver a Company Tax Return, which is the letter that makes a return due for a period. It quotes the UTR and the accounting period HMRC expects. What that notice means is in the CT603 notice to deliver a Company Tax Return.
Any other Corporation Tax correspondence: payment reminders, penalty notices, letters confirming dormancy.
The company's HMRC business tax account, if a Government Gateway account has already been enrolled for Corporation Tax; the UTR is shown against the Corporation Tax service.
Your accountant's records, if the company has ever had one. An agent authorised for the company holds its UTR.

Why it cannot be looked up

The UTR is not public. Companies House publishes a company's registered address, incorporation date, officers, filed documents, charges and previous names, and none of that includes anything from HMRC. That is why Dormant Return can autofill a company's name and number from the Companies House register as you type, but has to ask you for the UTR. HMRC's advisers will not give it out over the phone either: gov.uk's Corporation Tax contact page says plainly that they "cannot give you this reference over the phone".

Got the UTR? That is one of the three things a dormant company needs to file. Dormant Return prepares the CT600 and iXBRL dormant accounts and files them to HMRC under your own Government Gateway sign-in for £5, refunded automatically if HMRC rejects the return.

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How to get a copy if it is lost

HMRC has an online service, linked from gov.uk's "Find a lost UTR" page, to ask for a copy of a Corporation Tax UTR. Its rules, as stated on the service:

You give the company registration number and the registered company name; nothing else is asked for.
It only works for a company registered with Companies House.
The UTR is sent by post to the company's registered address as shown at Companies House, "to keep your details secure". It is not emailed or shown on screen, so make sure that address is one you can collect post from before you ask.
It cannot be used for a company that has been dissolved or struck off, or that changed to a different type of organisation. For a company incorporated very recently the service says to wait, because the original UTR letter should be on its way.

No timescale is given for the copy. Given that the letter goes by post, allow a couple of weeks, and if a filing deadline is close, request the copy before doing anything else; the penalty ladder in late CT600 penalties for dormant companies does not pause for lost paperwork.

Then, the sign-in

The UTR alone does not let you file. The company also needs a Government Gateway account with Corporation Tax added and activated against that UTR, a separate step with its own postal code. If someone else in the business set the account up and added you as a team member, the administrator also has to give you access to Corporation Tax. If the company has never filed online itself, do that next: enrol for Corporation Tax online before you file a CT600. With both in hand, the filing itself takes minutes; the walkthrough is in how to file a dormant company CT600 online.