If you currently have GST or any other form of Tax enabled, your Tax Invoice headings will look similar to this:
It is possible to remove all mention of 'Tax' from your receipt.
This is done by changing the name of your existing Tax Rate to 'NONE' (or creating a New Tax Rate as NONE).
Navigate to the following—
Admin > Lists > Select Tax Rates from the Select List drop down menu > Edit the relevant tax rate > Update Tax Name to NONE > Save.
NOTE: Tax Name is case sensitive, so you need to enter NONE fully capitalised as shown. If it is entered as 'none' or 'None' it won't trigger the removal of tax.
Once you have saved your NONE Tax Rate, invoices will no longer mention tax: