SimpleReturns

HMRC error 1046: why your sign-in was refused and how to fix it

Updated 15 July 2026
The short answer

Error 1046 is HMRC's way of saying "that sign-in did not match this company". It is nearly always one of four small things: a typo in your Government Gateway user ID or password, a wrong digit in your company's 10-digit tax reference (the UTR), Corporation Tax not yet switched on in that account, or Corporation Tax sitting in someone else's account, like an old accountant's. None of them mean you have done anything wrong, and each has a straightforward fix. One warning before you touch anything: do not keep retrying the same details, because three wrong tries can lock the account.

Official source. This guide is a plain-English summary of official GOV.UK guidance, not advice. The authoritative source is Sign in to HMRC online services on gov.uk. Always rely on that over our summary.

What does error 1046 actually mean?

On screen HMRC calls it an "Authentication Failure" and says your details "failed validation for the requested service". That sounds alarming, but in plain English it just means three things did not line up: the sign-in you used, the company tax reference you gave, and the Corporation Tax record HMRC holds. If any one of the three is off, even by a single character, HMRC turns the whole submission away with this code.

It is not a judgement on your return. Your figures have not been looked at yet. The door simply did not open.

Check this first: can you sign in at gov.uk?

Before changing anything, open HMRC's sign-in page on gov.uk and try signing in there with the exact same user ID and password. This one check cuts the problem in half:

  • If you cannot sign in at gov.uk either, the problem is the sign-in itself. Go to cause 1 below.
  • If you can sign in fine, your ID and password are good. The problem is the tax reference or which account holds Corporation Tax. Go to causes 2, 3 and 4.

Do not keep retrying. Three wrong tries can lock the HMRC account, and unlocking it takes longer than fixing a password. If a try fails, stop and check the details instead of guessing again.

What are the four causes, and how do I fix each one?

Work through these in order. Most people find their answer at step 1 or 2.

1. A typo in your Government Gateway user ID or password

The user ID is a string of characters HMRC gives you, and it is easy to mix up with another one, especially if you also have a personal account for your own tax. Your personal account is not your company's account. Corporation Tax lives in a separate business tax account.

The fix: find the email or letter HMRC sent when the business account was created, and copy the user ID from there character by character. Check you are using the company's business account, not your personal one. If the sign-in details are lost, see our guide on getting back into a lost Government Gateway login.

2. A wrong digit in your company's UTR

The UTR is your company's 10-digit tax reference. One swapped or missing digit is enough to trigger error 1046, because HMRC cannot match the return to your company.

The fix: check the number against a letter from HMRC, such as a notice to file or a payment reminder, rather than against memory or an old spreadsheet. Count the digits: there should be exactly 10. If you cannot find any letter, your company can request a copy of its UTR online and HMRC posts it to your registered office. Our guide on finding your company UTR walks through it.

3. Corporation Tax is not switched on in that account yet

Your sign-in can be perfect and your UTR correct, and HMRC will still say no if Corporation Tax has never been added to that account. Having a business tax account is not the same as having Corporation Tax switched on inside it.

The fix: sign in to the business tax account on gov.uk and add Corporation Tax to it using your company's UTR. HMRC then posts an activation code to your registered office, which usually takes a few days to arrive. Our guide on activating Corporation Tax online covers each step.

4. Corporation Tax lives in someone else's account

This is the sneaky one. Corporation Tax can only be switched on in one Government Gateway account at a time. If an old accountant or a former director set it up in their account, it stays there until HMRC moves it. That is why a perfectly good sign-in of your own can still be turned away: your account simply does not hold the company's Corporation Tax yet.

The fix: ring HMRC's Corporation Tax helpline on 0300 200 3410 and ask them to move Corporation Tax to your account. Have your company's UTR and company details ready. You do not need the old accountant's permission; HMRC can move it for you.

How long does each fix take?

Be honest with yourself about the clock, especially near a filing deadline:

  • A typo (cause 1): minutes, once you have the right details in front of you.
  • A lost sign-in: recovering a user ID or password can be same-day.
  • A wrong UTR (cause 2): minutes if you have an HMRC letter. If you need a copy posted, allow a few days.
  • Switching Corporation Tax on (cause 3): the activation code comes by post to your registered office, so allow a few days before you can file.
  • Moving Corporation Tax from someone else's account (cause 4): a phone call to start, then some waiting while HMRC does the move.

The lesson: if your deadline is close, start the fix today. A late Company Tax Return costs £200 from the very first day.

Common questions

Have I done something wrong?

No. Error 1046 is a matching problem, not a mistake in your return. HMRC has not even looked at your figures yet. One of four small details did not line up, and all four are fixable.

I have typed my password wrong twice. Should I try again?

No, do not risk a third try. Three wrong tries can lock the account, and unlocking takes longer than resetting a password. The safer move is to reset your password now and sign in fresh with the new one. Our guide on getting back into a lost Government Gateway login shows you how.

An accountant used to file for us. Is that why I am locked out?

Very possibly. If your old accountant set up Corporation Tax in their own account, it is still sitting there, and your sign-in will be refused no matter how correct it is. Ring HMRC's Corporation Tax helpline on 0300 200 3410 and ask them to move it to your account.

Can I just use my personal Government Gateway account?

No. Your personal account handles your own tax, like Self Assessment. Your company's Corporation Tax lives in a separate business tax account, and that is the one your filing has to go through.

Do I need an accountant to fix error 1046?

Usually not; all four fixes are things you can do yourself with a letter from HMRC and, at worst, one phone call. If your company's affairs are unusual, for example a dispute over who controls the old account, an accountant or a call to HMRC is genuinely the right move, and there is no shame in that.

Stuck at the connect-your-company step?

SimpleReturns has a rescue wizard built into exactly this step. It checks your sign-in first, before anything is submitted, walks you through the same four-cause diagnosis on this page, and gives you a before-you-start checklist so the posted-code delays never catch you by surprise. It is free to start, no card needed, and filing costs £99 flat per submission.

Start your return

And if HMRC needs to move Corporation Tax between accounts, that part is a phone call to HMRC that no software can do for you; we tell you that plainly rather than pretend otherwise.

General guidance, not advice. This guide explains how the rules generally work for small UK limited companies. It isn't tax advice for your specific situation, if you're unsure, check with us or an accountant.