If you've created invoices that do not have GST, but they need to, here's how to fix it:
- Go to Reports (Take me there).
- In the search field, enter Transaction List by Date.
- Select Customise.
- Select the correct date range.
- Under Rows/Columns, select Change columns.
- Select GST.
- Select Run Report.
- Select each invoice that's missing GST, add the GST, and then select Save.