Knowledge Base

Find out how and why

How to resolve the 1046 Authentication Error

Steps to take to resolve the 1046 Authentication Error that you get if your HMRC Credentials are invalid or incorrectly setup

How to resolve the 1046 Authentication Error

If you are receiving a 1046 error message after submitting your CT600, to the HMRC gateway this is because the details entered when attempting to file are incorrect, or they do not match what HMRC are expecting. The EasyDigitalFiling Service sends your UTR together with User ID and Password exactly as you have entered these.

To resolve this error message, please go through the steps below.

Step 1 - Check that your UTR is correct

A UTR or Unique Taxpayer Reference is a number that is unique to you (the legal entity) Assigned by HMRC. This number is 10 Digits - Please ensure that you have entered it correctly with no spaces. You can validate that your UTR is correctly formed on this page What is a UTR Number

Step 2 - Check that your HMRC User ID and Password are correct

This may seem obvious however its very easy to enter numbers incorrectly when reading from a form. Check that there are no transposed values and there are no spaces.

Step 3 - Validate your User ID and password

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 on-screen 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 more information on the HMRC website ( Alternatively, contact HMRC directly to resolve this.

Please note: If you contact 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 4 - Check that your account has the filing service added

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

After logging into your HMRC account as a new user, you will presented with a list of services. To register for coporation tax you will require your UTR and either your Companies House Registration Number (CRN) or your registered office postcode. You will then be sent an activation code by post. For individuals 'Self Assessment' should be 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 add service, you will need to wait for an activation code to be sent via post once received 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. Please note that you have 3 attempts to enter the code otherwise you will be locked out and have to request another.

If you are filing for a partnership (SA800), 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.

This article is information only and has been prepared for general guidance on matters of interest only, and does not constitute legal, accounting, tax, investment or other professional advice or services. You should not act upon the information contained in this article without obtaining specific professional or legal advice. No representation or warranty (express or implied) is given as to the accuracy or completeness of the information contained in this article, and, to the extent permitted by law, Comdal Limited, its members, employees and agents do not accept or assume any liability, responsibility or duty of care for any consequences of you or anyone else acting, or refraining to act, in reliance on the information contained in this publication or for any decision based on it.