Hello, ScottD1.

Bi-monthly schedule is currently unavailable in QuickBooks Australia. The current schedule you can select are Monthly, Quarterly, Half-yearly and Yearly. 

You might want to reach out to ATO so you can get the best filing period for your type of business. 

For additional information about changing frequencies, please check out this article: https://quickbooks.intuit.com/community/GST-and-BAS/How-to-change-lodging-frequencies-in-the-GST-Cen...

Stay around if you have other questions about QuickBooks.