Hi glenn27,
Thanks for posting in the Community!
Are there any previous BAS lodgements in QuickBooks Online? If the BAS has been lodged outside QuickBooks Online you can lodge it and select Mark as lodged. However, if you would like to reset the GST to lodge in QuickBooks Online, you can contact our support team to unlodge it for you.
Feel free to post again if you have any other questions. Have a great day!