SBR validation error CMN.ATO.AUTH.011 in HandiTax states that the client isn't linked to your agent profile on the ATO portal, the ABN entered for the client has been cancelled, or the ABN is incorrect.
Log in to your ATO portal and check that the client is linked to your Tax agent number. If the client has been added, but does not appear, remove them and then add them back.
If an ABN is entered in HandiTax, add the ABN on the ATO portal.
Check if the TFN and ABN match in HandiTax and ATO portal.
Check the ABN has not been cancelled: ABN Lookup.
If you have recently processed a CU (Client Update) form for a Trust, ensure you have removed The Trustee For wording from the Trust name. See Why is the client update form being rejected for a family trust for more information.
You can create a Client Update (CU) Form for your client individually, or create in bulk under the Client menu, then click, Batch create Client Update forms.
Note: Contact the ATO for advice specific to your client's circumstances.