This error means that HMRC cannot find any business linked to the NI number provided.
To resolve this, check the following:
Ensure the individual is registered as self-employed with HMRC.
Confirm they have signed up for the appropriate HMRC service (e.g., Making Tax Digital, if applicable).
Verify the correct HMRC login credentials are being used.
If the NI number is correct and the issue persists, it usually indicates a mismatch between the NI number and HMRC records.
For sole traders, log in to the HMRC account and check that the self-employed business is visible and linked to the NI number before retrying.
If the client only has rental/property income and is not operating a self-employed trade, selecting "Property Business (UK)" may be more appropriate than "Sole Trader," but this must match the HMRC registration type.