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HMRC rejected my sign-in details but they are correct

Last updated: 12 October 2026

Short version. When HMRC refuses your CT600 with an Authentication Failure, that return was not filed. This guide finds which of five causes it is and shows how to send the return again. You are probably right that your details are correct, and HMRC is also right to refuse them. HMRC sends one identical error for five different problems, and only one of them is a wrong password. The usual cause is that your Government Gateway user ID, your password and your company’s Unique Taxpayer Reference (UTR) are each correct on their own but do not all belong to the same HMRC account. Signing in to HMRC and looking at what that account contains tells you which of the five it is.

Go to the steps and entry details

On this page

HMRC Authentication FailureReturn not filedWhere you see it: After you submit › Gateway submissions

Before entering figures, the filing setup questions can set the existing destination and CT600 route for an ordinary limited company. They keep the full accounts dates beside the CT600 dates. You can also continue with the controls below without opening the questions.

What this guide covers

When HMRC refuses your CT600 with an Authentication Failure, that return was not filed. This guide finds which of five causes it is and shows how to send the return again.

  • The filing page reads Gateway details and UTR not accepted and the CT600 shows Rejected. HMRC's message is “Authentication Failure. The supplied user credentials failed validation for the requested service.”
  • You will not be charged again to resubmit once it is sorted.
  • For an accounts period over 12 months, both CT600s are sent with the same details, so the error usually shows on both. Two CT600s for a long period
  • This is about HMRC only. If Companies House was also a target, check its row separately. It uses the company authentication code, not these details.

Is this the right guide for you?

Use it if all of these are true

  • You submitted a CT600 to HMRC with us.
  • The filing page reads Gateway details and UTR not accepted, or the HMRC row shows the Authentication Failure message.
  • You are sure, or fairly sure, the user ID and password are typed correctly.

Do not use it if

Why one error means five different things

When HMRC refuses a Corporation Tax submission for its sign-in details it returns “Authentication Failure. The supplied user credentials failed validation for the requested service”. That single message covers all of these:

  • The Government Gateway user ID or password genuinely has a typo.
  • The user ID and password are right, but that account has never had Corporation Tax added to it.
  • Corporation Tax was added, but the service was never activated with the activation code HMRC posted out.
  • The account has Corporation Tax activated, but for a different company than the UTR you are entering.
  • You are signing in to a personal tax account rather than the business one. Plenty of people have both, with different user IDs.

Common mistake: trying the password again

Because the message is the same in all five cases, entering the same password again cannot tell you anything, and the next submission is refused in the same way. Look at the account first. On the filing page, the HMRC row links to this guide with How to check which it is.

Worked example

Company
Yew Example Ltd
Accounts period
1 October 2024 to 31 December 2025 (15 months, so two CT600s)
What happened
The director runs two companies and entered the user ID set up for the other company. Both CT600s showed Rejected.
What the director found
Signed in with that user ID, Corporation Tax was listed with the other company’s UTR
The fix
Signed in with the user ID that lists Yew Example Ltd’s UTR, then sent both returns again with that user ID and its password

The company and all figures on this page are fictional.

Before you start

The user ID you entered
You need to sign in with exactly that user ID and its password.
The company’s UTR
Ten digits, on HMRC letters such as a notice to file. Where to find your UTR
Time
Checking the account takes a few minutes. Adding or activating Corporation Tax needs a code HMRC sends by post.

The company and all figures on this page are fictional.

Check which account you are actually signed into

  1. Sign in to HMRC using the Government Gateway user ID you entered for this filing. If sign-in fails, HMRC tells you how to recover or reset your details.
  2. Check that Corporation Tax is listed and that the company’s UTR matches the filing.
  3. If the service is missing or not yet activated, add it and activate it before you try again.
  4. Return to the rejected filing, enter the correct details and send it again. Send the return again Use an amendment only when correcting a return HMRC has accepted.

Go to gov.uk/log-in-register-hmrc-online-services and sign in with the same user ID and password you gave us. Two things to note once you are in:

  • The user ID you signed in with. This is what has to match Gateway User ID in your filing. Government Gateway user IDs are up to 12 characters.
  • Whether this is the business account. If you see Self Assessment or your own personal tax and no Corporation Tax at all, you are in a personal account. The company’s Corporation Tax will be on a different user ID.

If you cannot sign in at all, the problem really is the user ID or password, and HMRC shows you how to recover either when you try to sign in. Too many wrong attempts lock the account for 2 hours.

When entering Gateway User ID in the filing window, spaces copied with the ID are removed automatically. Letters, digits and punctuation stay as entered. The password is used exactly as you enter it, including any spaces. If your period needs two Corporation Tax returns, the same Gateway ID is used for both.

Check the UTR is added to that account, and activated

Still signed in, look for Corporation Tax in the services on the account. Three separate things have to be true:

  • Corporation Tax is listed. If it is not there, this account is not enrolled for it and cannot file, however correct the password is.
  • The UTR matches the UTR you are entering. If the account shows a different number, you are filing for one company with another company’s account.
  • It is activated. After you add Corporation Tax, HMRC posts an activation code to the registered office within 10 days. Until you activate the service with it, the account cannot file. If the code did not arrive or has expired, you can request a new one.

Our guide to setting up a Government Gateway account for Corporation Tax covers adding Corporation Tax and the activation code step by step.

All three have to match on the same account

This is the part that catches most people. It is not enough for each detail to be correct somewhere. To file, all of the following must be true at once:

  • the Government Gateway user ID and password sign in to one particular account,
  • that account has Corporation Tax added and activated,
  • and the UTR on that account is the UTR of the company you are filing for.

If you run more than one company, the most common version of this is using the Government Gateway user ID for company A while filing for company B. Check you are using the user ID that lists this company's UTR.

If the UTR is missing, or is not your company’s

There are three versions of this, and they need different fixes.

  • Corporation Tax is not listed on the account. Add it, then activate it with the code HMRC posts to your registered office. GOV.UK says the code arrives within 10 days, so do not leave this until your deadline. GOV.UK: how to add Corporation Tax services
  • A different company’s UTR is shown. You are in the wrong account for this filing. Sign in with the Government Gateway user ID that lists the company you are filing for, or add Corporation Tax for it.
  • You do not know the company’s UTR, or think it is wrong. It is the 10-digit number on HMRC letters about Corporation Tax, such as a notice to file a Company Tax Return or a payment reminder. It is not your personal UTR and it is not the Companies House registration number. Where to find your company UTR

If the UTR should be on the account and is not, or HMRC has it against the wrong company, only HMRC can put that right. For technical problems with HMRC online services, HMRC's online services helpdesk is on 0300 200 3600. GOV.UK: technical support with HMRC online services

Send the return again

  1. Open the rejected filing

    Filing page
    Click Re-submit to HMRC → beside the rejected return or at the top of the page
    Or from the company page
    Click Re-file CT600

    Both open the Review & file page for the same filing, with only HMRC selected.

  2. Review & file

    Continue
    Click Continue to submission

    If your figures need to change too, the filing page also offers a link back to the wizard. Rejected filings

  3. Filing credentials

    Filing targets
    HMRC ticked
    Corporation Tax UTR
    The UTR the account lists for this companyAlready filled in from the filing. Correct it if it was wrong.
    Gateway User ID
    The user ID of the account that lists that UTRThe field starts empty each time.
    Gateway Password
    The password for that same user IDThe field starts empty each time.
    Select the director submitting this return
    The director submitting the return
    Declaration
    Tick it

    Click Submit to HMRC.

    More help: Gateway User ID and Gateway Password explained

Two CT600s for a long period

When your accounts period ends more than 12 months after it starts, even by one day, HMRC needs two CT600s. You enter the UTR, user ID and password once, and we send both returns with those same details, one after the other.

  • Each return has its own row on the filing page, numbered like Return 1 of 2, with its own status.
  • The second return is still sent when HMRC refuses the first. Because both used the same details, an Authentication Failure usually shows on both rows.
  • Re-submit to HMRC → sends both CT600s of the period again, including any return HMRC has already accepted. What a repeat of an accepted return means
  • With File only the remaining CT600, only the second CT600 was sent, so only that one is sent again.

Sample outcome

Nothing filedA return refused with an Authentication Failure is not filed with HMRC.
Both returns againFor Yew Example Ltd, both CT600s are sent again with the corrected user ID.Two CT600s
No second chargeSending a rejected filing again does not cost more.

If it still fails

If Corporation Tax is listed against the right UTR, it is activated, and the submission is still refused, contact us and tell us:

  • the Government Gateway user ID you are using,
  • the UTR shown against Corporation Tax in that account,
  • and that the service shows as activated.

Never send us your Government Gateway password. We do not need it to investigate, we will never ask for it, and you should not share it with anyone. You enter it yourself in the filing dialog each time you submit.

You can also see the response HMRC gave on your filing page, along with what error 1046 and other HMRC codes mean.

This article is general guidance, not tax advice. If HMRC’s records for your company look wrong, HMRC is the only party that can correct them.

More help: GOV.UK: help with signing in to HMRC online services

Not the right guide?

Open the guide for the detail you need.

Setting up a Government Gateway accountAdd Corporation Tax and activate it.Where to find your company UTRThe 10-digit Corporation Tax reference.Companies House authentication codeIf Companies House refused your accounts.

Looking for a different field or step? See all filing wizard guides →

Official sources

Whether this route matches your filings is for you to decide, yourself or with your accountant.

Example companies and figures are fictional. Field names match the filing wizard as of 12 October 2026.