SA800 Authentication Error

An Authentication Error means that the HMRC Gateway ID and password were rejected by HMRC. This can be caused by a typo in the Gateway ID or password, or it can mean that the Gateway ID does not have permission to submit for the UTR in the return.

That could be because the Gateway ID is linked to a different UTR (e.g. for an individual, or a different partnership) or it could be because the Gateway ID hasn't had the Self Assessment service activated.

Note that for an SA800 Partnership return, the Gateway ID must be linked to the partnership ; you cannot use the Gateway ID used by a partner to submit their individual Self Assessment. If you don't have a Gateway ID for the partnership, to create one:

1. Go to the sign in page for the HMRC website: https://www.gov.uk/log-in-register-hmrc-online-services and click 'Create sign in details'
2. Click 'Create sign in details' then follow the prompts
3. That will create a fresh government gateway ID (you can create multiple using the same email address without any issue) with a password that you set during the process.
4. After you obtain the gateway ID you can then select a type of account for it - select 'Organisation'
5. On the Business Summary screen that appears click 'Add a tax, duty or scheme' then 'Self Assessment, including partnerships and trusts' and follow the prompts.
6. HMRC will then put an activation code in the post to the UK address you provided.
7. When that arrives, sign in to the HMRC website as instructed, to enter that code to complete the activation process.

Suggested steps if you are seeing an Authentication Error when you try to submit:

1. Use the 'Show' button in the 'Submit' popup to look at the password you have entered
2. Re-check that UTR number you have entered in 'Partnership information' in ABC SA800 Partnership Tax Return is the correct one for the partnership
3. Sign in to the HMRC website https://www.gov.uk/log-in-register-hmrc-online-services using the credentials you are entering in to ABC SA800 Partnership Tax Return
4. Look for a 'Self Assessment' section; if that displays instructions on how to enrol for Self Assessment, follow the link and instructions, which will trigger HMRC to put an activation code in the post. When that arrives, follow the instructions to complete activation.

Finally, some users find that, without realising it, they have multiple Self Assessment username/passwords and are using the wrong one. This only comes to light from talking to the HMRC online Self Assessment helpline.