The error 1046: Authentication Failure is generated from HMRC's end and we can only help you with possible reasons for this. Please check the HMRC Credentials and UTR Number.
For complete details you may also see below:-
1. 1046 - Authentication Error - The Government Gateway has told you that either your user ID, password, PAYE office number or PAYE reference number are incorrect. Capium is not aware about your HMRC User ID and Password and simply sends this information to the Government Gateway. If you see this error message, then it means that the Government Gateway have rejected one or more of these items.
Whilst we can't tell you what these details should be, we can tell you some of the most common mistakes that lead to a rejection. These are as follows:
- The length of your ID or password. Government Gateway IDs are 6 to 12 characters long (a combo of letters and numbers) and the Passwords are 8 to 12 characters long (a combo of letters, numbers and special characters). Check that you have not entered too many characters. If you think that your ID or password should be 13 or more characters long, then try using the first 12 of those characters.
- Typing errors in the ID and Password e.g. using 1, I or l (the number one, capital letter I, lower case letter l) incorrectly, or using O instead of 0 (letter O, digit zero) or vice versa.
- You 'copied and pasted' your ID and password from somewhere else. Try deleting and re-entering these details using keyboard.
- Incorrect HMRC reference entries such as wrong PAYE Info, wrong UTR Number, wrong Company Registration Number (CRN). Check that you haven't entered your details incorrectly e.g. '123/M5656' instead of '123/M6565' etc.
- You have recently (within the last couple of weeks) activated your new ID and password. - It generally takes around 2 weeks for your new ID and password to become active across all HMRC systems.
If you have checked and re-checked all of these things and still receive the error message then you will need to contact HMRC online services helpdesk (0300 200 3600). Please be aware that we have no idea what your ID and password should be.