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What is a 1046 authentication error?

When you receive the 1046 error message, this is because the details entered when attempting to file are incorrect, or they do not match what HMRC are expecting. To go through this error message, please see the below instructions or download our PDF step by step guide

Step 1: Check User ID and password are correct for the HMRC website

  1. Go to the HMRC Login page:
  2. Enter your User ID and Password, then log in. 

If successful, you will be presented with a security message (click on Next to carry on).

If unsuccessful, you will receive an error message and will need to follow the onscreen instructions to reset your username and/or password.

If you have already tried to log in three or more times, then HMRC will have locked your account for two hours and you will therefore need to wait before trying again.

You can find further information on the HMRC website ( Alternatively, you can contact HMRC directly to resolve this.

Please note: If you are in contact with HMRC, you should ensure that you have a Government Gateway account and not a gov.verify account, as the latter account type will not currently allow you to file online. 

Step 2: Check that you have added the Self Assessment service to your HMRC account

In order to file online, you have to associate your filing credentials with your UTR. This is done by adding the Self Assessment service to your account.

After logging in, you will be presented with either the ‘new style’ HMRC page or the ‘old style' HMRC page:

Old style page (logo is HMRC Revenue & Customs)

  1. Toward the bottom of the page, there is a section labelled ‘Services you can use’ - click on ‘Activate or access online services’.
  2. ‘Self-Assessment (SA)’ should appear in the list, along with the UTR that you are trying to file against.

New style page (logo is

After logging in, you will be taken to a list of services you can use automatically. 'Self-Assessment' should appear as the first item in the list, along with the UTR that you are trying to file against.

If the UTR is not displaying in either of the locations above, then you haven’t added the Self Assessment service to your account. You will need to do this before you can use these credentials to file online.

After selecting to add the service, you will need to wait for an activation code to be sent via post and this code needs to be entered into HMRC's website. In some instances, you may need to wait 24 to 48 hours after activation before trying to file to HMRC.

Note: If you are filing for a partnership, the partnership will need its own set of filing credentials with the service added so that it displays that UTR rather than the UTR for the partner. 

Step 3: Check credentials entered into TaxCalc

Steps 1 and 2 confirm that your User ID and password are correct and that you have activated the Self Assessment service on that account.

You will then need to:

  1. Open your tax return in TaxCalc.
  2. Remove and re-enter the UTR, User ID (this should be 12 digits long and contains a mixture of letters and numbers) and password (tick ‘Show password’ to see the password as you type it).
  3. Re-submit the return by going to Check and Finish > File Online > Re-submit

If you still receive a 1046 error, there may be a block on your account at HMRC. You will need to call them on 0300 200 3600 (International: +44 161 930 8445) to resolve this.