The prefill data shows that the taxpayer is only eligible for the Simple BAS reporting method. This means the G2, G3, G10 and G11 fields do not apply and are correctly disabled.
An issue has been identified where the incorrect reporting method is selected, and you are unable to choose the Full reporting method.
This issue has been resolved in Tax release 2026.2.0.
You will need to be delete and recreate the Bas after you install the update.
The new release also includes:
A new field that shows the reporting methods the ATO has made available for each statement.
Restrictions that limit reporting method selection to only those allowed by the ATO. This is determined by the ATO and is unable to be changed.