Invoices mistakenly created without GST

If you've created invoices that do not have GST, but they need to, here's how to fix it:

1. Go to Reports (Take me there).
2. In the search field, enter Transaction List by Date.
3. Select Customise.
4. Select the correct date range.
5. Under Rows/Columns, select Change columns.
6. Select GST.
7. Select Run Report.
8. Select each invoice that's missing GST, add the GST, and then select Save.