LodgeiT

If Varying "T7- Instalment amount", user can only fill:

 T8 - Estimated Tax for the year

 T9 - Varied amount payable for the quarter

and T4 - Reason code for variation

But, the PAYGI Option and Instalment amount (T7)  are not allowed by ATO to be changed and should be reported as is.

Related Guide:

BAS "Instalment Amount" T7 (PAYGI)

Note:

If the IAS form is past due, you won’t be able to vary the installment amount. In such cases, please contact the ATO. If the ATO is unable to assist, please make the necessary adjustment at year-end.