Error codes you might receive when submitting your Corporation Tax return

This article provides a list of error codes you may receive from HMRC when filing your Corporation Tax return (CT600), along with suggested steps to take to resolve them.

When you submit Corporation Tax to HMRC through FreeAgent, you’ll receive an error code if HMRC rejects your submission. Below is a list of error codes that you may receive and how to resolve them:

• 1046: authentication failure
• 1608: incorrect UTR number
• 1611: known facts check
• 3001: invalid information submitted
• 3304: duplicate accounts submitted

Making corrections

When you finalise your company’s End of Year report by adding your signature, this places an initial lock on your accounts to prevent you from making any further changes.

In order to make changes, you would need to remove the lock on your End of Year report by removing your signature. Please note that you can only remove this lock to make changes if you haven’t yet filed your Final Accounts or Corporation Tax return through FreeAgent.

If you’ve filed either of these through FreeAgent, you’ll no longer be able to remove this lock on your accounts. Find out how to make corrections in each of these scenarios, including when both Final Accounts and Corporation Tax returns have been filed.

Removing your signature

To remove your signature from your End of Year report, navigate to the ‘Accounting’ tab at the top of the screen and select ‘End of Year’ from the drop-down menu.

Select ‘Remove signature’.

Select ‘OK’ in the pop-up window to complete the process.

You’ll now be able to make changes to your accounts and finalise your End of Year report again once you’re happy everything is now correct.

Error code 1046: authentication failure

This error code is the result of an authentication failure where HMRC does not recognise the Government Gateway credentials that you have entered.

This could be due to:

• an incorrect Corporation Tax reference (UTR) number
• needing new Government Gateway credentials if your accountant has been filing on your behalf
• Corporation Tax not being enabled as a service on your business tax account
• Government Gateway credentials being auto-filled incorrectly rather than entered manually

Find out more about how to resolve an authentication failure error message.

Please note that if you need to update any of your business’s details, such as your Corporation Tax reference number (UTR), you’ll need to remove your signature from your End of Year report first.

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.

Error code 1608: incorrect UTR number

This error code is a result of HMRC not recognising your company’s Unique Tax Reference (UTR) number.

A company’s UTR is a 10-digit number that HMRC issues to all new limited companies to identify companies for all tax-related purposes. You can find your UTR by logging in to your business tax account or requesting a copy to be sent by post from HMRC.

To update your UTR in FreeAgent, first remove your signature from your End of Year report, then select 'Settings' from the drop-down menu in the top-right corner and select 'Company Details'.

Please make sure that you're using your limited company UTR and not your personal UTR or that of any other individual such as a business partner.

Once you’ve entered the correct UTR in the ‘Corporation Tax Reference’ field, select ‘Save Changes’ at the bottom of the screen and try submitting your Corporation Tax to HMRC again.

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 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.

Error code 1611: known facts check

This error code is a result of submitting a Corporation Tax return as an amendment, but HMRC has no record of an original return having been submitted for that accounting year previously.

To resolve this issue, navigate to the Corporation Tax return in question and select ‘Edit Details’.

Select ‘No’ to ‘Are you making an amendment?’, select ‘Save Changes’ and try submitting your Corporation Tax return to HMRC again.

Error code 3001: invalid information submitted

This error code is a result of something invalid being submitted to HMRC. It will usually be accompanied by another error code that provides more information on the error, for example 1608 or 3304.

Error code 3304: duplicate accounts submitted

This error code is a result of a Corporation Tax return (CT600) for this accounting period having already been submitted and accepted for filing by HMRC outside of FreeAgent. This suggests that the tax return that you’re trying to file through FreeAgent is a duplicate return.