Making Tax Digital (MTD) VAT – Error 403: CLIENT_OR_AGENT_NOT_AUTHORISED

When submitting or retrieving MTD VAT data from HMRC, you may see this message in the Navigator:

HMRC server has returned an error message:
HTTP status: 403 (Forbidden)
Code: CLIENT_OR_AGENT_NOT_AUTHORISED

This means HMRC’s system has not authorised the software to access VAT data.
The message is sent directly from HMRC’s server, not generated by Navigator.

Why This Matters

This error prevents VAT data from being submitted or retrieved through MTD.
It usually means the HMRC registration or authorisation process has not been fully completed.

Cause

HMRC has returned the following error:
HTTP status 403 (Forbidden): CLIENT_OR_AGENT_NOT_AUTHORISED

This occurs when the client or agent is not authorised to submit or request MTD VAT data.

Common reasons include:

Business:

• The business has not signed up for Making Tax Digital for VAT.

• HMRC has not completed the registration process (can take up to 72 hours).

Agent:

• The agent has not created an Agent Services Account. This is different from the standard HMRC Online Services for Agents account.

• The agent has not linked clients to the Agent Services Account.

• The client has not signed up for MTD VAT.

• The client has not authorised the agent to act on their behalf.

• HMRC has not completed the registration process (can take up to 72 hours).

Solution

Step 1: Register with HMRC
Before authorising Navigator, ensure that the business or agent has signed up for Making Tax Digital for VAT and that HMRC has confirmed registration.
This confirmation may take up to 72 hours after sign-up.

HMRC provide step-by-step guides:

• Businesses: https://www.gov.uk/guidance/sign-up-for-making-tax-digital-for-vat

• Agents: https://www.gov.uk/guidance/sign-up-your-clients-for-making-tax-digital-for-vat

Step 2: Authorise the Software
Once registration is complete, use the VAT Digital Authorisation function in Navigator to authorise the software to interact with HMRC. You may need to contact helpdesk to assist with the reset.

This allows the submission and retrieval of VAT data under MTD.

Note:
Authorisation must be refreshed periodically.
After 18 months, the authorisation fully expires and must be renewed.

Step 3: If the Issue Persists
If the 403 error continues, contact HMRC’s Online Services Helpdesk on 0300 200 3701 and ask to speak with the MTD VAT team.

They can confirm whether your business or agent account is correctly registered and authorised for MTD VAT.

Navigator cannot access HMRC systems to check registration or authorisation status.

Related Error Messages

Other errors may appear when connecting to or submitting data to HMRC.
These messages are also generated by HMRC’s MTD VAT service and not by Navigator.