To resolve this error:
Ensure you have filled in the ABN in any section where you have entered data into the form where there may be mandatory ABN fields.
Reset the credential from the Lodgment menu, Set ATO Credentials.
even if these fields are already populated, click the ellipsis to re-select the keystore.xml file, re-select the credential from the drop-down menu, type in the password, click OK then restart HandiTax.
Please check that you are on the latest version of HandiTax 20XX.
If you have checked through and cannot resolve the error, please raise a new case online and reference the title of this article.