Corporation Tax error message: authentication failure

This article explains the steps to take if you've received an error message telling you there is a problem with your submission when trying to file your Corporation Tax return in FreeAgent.

If HMRC does not recognise the Government Gateway credentials that you have entered, you’ll receive the error message below when trying to submit your Corporation Tax return to HMRC.

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There can be a few other reasons for this error message. If you have full (level 8) access to your FreeAgent account, you can follow the steps below to identify and resolve the error.

1. Check that the Corporation Tax reference is correct

Select 'Settings' from the drop-down menu in the top-right corner and then select 'Company Details'.


Make sure that the ‘Corporation Tax Reference’ (also known as the COTAX reference or Company UTR) is correct. Please make sure that you're using your limited company UTR and not your personal UTR or the UTR of any other individual, such as a business partner.

If the Corporation Tax Reference is incorrect, update it with the correct number and select ‘Save Changes’. For more information on how to add or edit your business’s details, please see this article.


Please note that if you’ve already submitted Final Accounts to Companies House through FreeAgent, you won’t be able to update your UTR. In this scenario, our Technical Team can update your UTR if it’s incorrect. If you need our Technical Team to update your UTR in FreeAgent, please contact our support team by selecting the blue ‘Help’ button in the bottom-right corner of the screen.

2. Check whether you’ve previously filed Corporation Tax using the same Government Gateway credentials

If your accountant has previously filed Corporation Tax on your behalf using the credentials that you’re entering into FreeAgent, you may need to register for a new Government Gateway ID (HMRC online account) to file for the company yourself.

3. Check that you can log in to your HMRC online account using the Government Gateway credentials

Navigate to HMRC’s website to check if you can log in to your HMRC online account using the same Government Gateway credentials that you’re entering into FreeAgent. If you’re unable to log in, please see the following HMRC guidance.

4. Check that Corporation Tax has been enabled as a service

If you can log in to your HMRC online account, make sure that Corporation Tax has been enabled as a service. If it has, it should look similar to the image below.


If Corporation Tax hasn’t been enabled as a service, you’ll need to select ‘get online access to a tax, duty or scheme’ and follow the steps provided to add it. Please note that if you do need to do this, HMRC will send an activation code out in the post which can take up to 10 days to arrive. Once you’ve successfully enabled online filing, you’ll see a notification advising of return deadlines.


If you haven’t filed a Corporation Tax return yourself before, for example if your accountant was doing this for you previously, you may need to log in to your HMRC online account and authorise Corporation Tax as a service.

5. Check that you’re entering your Government Gateway credentials manually

When submitting your Corporation Tax return through FreeAgent, make sure that your Government Gateway credentials are being entered manually and not being auto-filled by your browser.

If any of your details are being auto-filled, you should delete the auto-filled information and enter your Government Gateway ID and password manually instead, just as you would enter it to access your HMRC online account.

In the majority of cases, the authentication failure error message is caused by Corporation Tax not being enabled as a service on the HMRC online account, the credentials in FreeAgent being auto-filled or not being the same credentials used to access the HMRC online account.

If you continue to receive the error message after completing the troubleshooting steps above, please check with HMRC directly. As the error message has been sent from their system, they will need to investigate.

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