Hi, SueP1
Thanks for your post, and Welcome to the MYOB Community Forum.
If you wish to change the ATO Reporting Category of your Payroll Category, you can undo the finalisation by going to Payroll Reporting Centre > EOFY FInalisation tab > Tick the employee's name then undo the finalisation. Once done, you can then change the ATO Reporting Category then send update event for the impacted payroll year. After that, you can redo the finalisation.
However, since the Tax Returns have been lodged already, it is best to speak with the ATO first before making any changes.
Please let us know if you require any further assistance with this.
Best regards,
Doreen