This error occurs when you are reporting a GST Installment (Option 3) and it includes the following fields.
G1 - Total sales
G2 - Export sales amount
G3 - Other GST-free sales
G10 - Capital purchases
G11 - Non-capital Purchases
GST included in total sales indicator (G1 includes GST)
To solve the issue:
Change the GST reporting option to 2
At Does the amount shown at G1 include GST?, untick N.
Change the GST reporting to option 3
Re-enter the amount at G21.
Save and close the return.
Lodge the return.
