Let me show you how to lodge your BAS in QuickBooks Online.
Go to GST tab and select Prepare BAS. If this is the first BAS to be lodged, selected Get Started and enter the date of the BAS to be lodged.
You can check the amounts showing on the taxes you've enabled and select Next.
After reviewing the complete activity statement, select Mark as lodged to close the tax period in QuickBooks. If you've enabled BAS e-lodgement, you will see a Lodge with ATO option.