HMRC “Authentication Failure”

Check you have entered the correct credentials


Make sure your credentials are entered correctly. See Online Filing Passwords.You may have different credentials for CT and SA filing so make sure you have entered the correct ids. You must ensure you are using valid agent credentials and not client credentials. You do NOT need valid authorisation for the client to file (e.g. 64-8), but you must be using valid credentials for the correct service.


Please make sure you are using the correct id and password for the return you are filing.

Authentication errors can sometimes be cleared by changing your password to a password containing between 10 and 12 letters only, no numerals, capitals or punctuation. Once you have successfully filed your return we recommend that you change your password back to a more secure and memorable password.

You cannot use an individual’s id and password to file a partnership or trust return – they must have their own id and password.

Check that you have entered the correct UTR

If the UTR is incorrect you should unlock the tax return submission before changing it.