Hi there, Duncan. QuickBooks Online calculates GST automatically for each line item, but it’s designed to display the tax rate per line and the total GST amount at the bottom of the invoice. Currently, there is no option to display the GST amount per line directly on the invoice template.
In the meantime, you can include the GST amount in the Description field for each line item. To enable this, open your invoice, select "Manage," then "Customisation," and under "Table content," toggle the "Description" field on. Once enabled, you can manually enter the GST amount alongside each line. This allows you to reflect the GST amount alongside each charge while keeping the system’s tax calculation intact.
Note: These steps apply when using the modernised invoice layout. If you’re using the classic view, the customization options may appear differently.

If you have further questions, please reply in this thread.