If you receive a response stating 'client or agent not authorised' when trying to file a VAT return or an MTD Income Tax (IT) quarterly submission, it will be due to at least one of the following reasons:

• HMRC user ID and/or HMRC password used to authorise and obtain a 'token' in TaxCalc is incorrect
• The business and/or client has not been signed up for MTD VAT or IT
• VAT registration number is incorrect
• NI number is incorrect
• Postcode is incorrect
• Agents - authorisation to act on behalf of a client does not exist

To troubleshoot :

• Check that you can log into your government gateway account (or agent services account) using your HMRC user ID and password and make sure that the business (or client) is enabled to submit VAT returns/MTD for income tax for the business (or client business).
• When in the government gateway or agent services account, check that the following match the details held in TaxCalc:
  • VAT registration number
  • NI number
  • Postcode
• Check that a current HMRC 'token' exists for filing in Taxcalc. These can be retrieved within Admin Centre > Applications > VAT Filer or MTD Quarterly Filer.

If you have checked all of the above are and the error still appears please call HMRC on 0300 200 3700 in the first instance as it is more likely to be an issue with the online account, if all the details have been entered correctly in TaxCalc.

For tax return submissions with an authentication error please read the article What is a '1046' Authentication Error?