I am getting error 1046 when I send data to HMRC. What could be wrong?

This means 'Authentication Failure. The supplied user credentials failed validation for the requested service'.

The possible reasons for this error are:

• User ID is wrong.
• Password is wrong (Try logging in at the HMRC site).
• You registered your HMRC account for PAYE but haven't yet received the activation PIN.
• The PAYE Reference on the Employer Details page is wrong (Log in to the HMRC site to see what reference they hold).
• The User ID is for a different business.
• Most symbols on a UK keyboard are fine, but if your password contains £, € or ¬, these non-ASCII characters can cause problems.
• Government systems are too busy.