Sorry, HMRC changed the URL of their login so the link in the authentication wizard is broken. We apologise for that, but effectively by going to online.hmrc.gov.uk/login you're doing the checks that we suggest.

At least one of the 4 values on the authentication wizard is incorrect:

• Gateway login
• Gateway password
• Tax office
• Tax reference

Through the years we've been told a large number of times by people that they're getting the authentication error when all 4 things were correct. Every single time, when they've given up and we've investigated it, we've found that they were mistaken, and that they'd entered one of the 4 things incorrectly.

Errors to watch for:

• Transposed digits
• Using payment reference rather than tax reference
• Gateway login that isn't 12 letters/digits long
• Gateway password that is more than 12 letters/digits long
• Gateway login and tax reference are both correct, but that login doesn't have that tax reference attached to it
• Gateway login and tax reference are correct, and tax reference has not yet been activated against the login
• 1, I, and l mixed up
• 0 and O mixed up
• Spaces on the end of login or password
• Entering the 12Pay website login rather than the HMRC online login code and password