I need to take of sales tax on an invoice as we don't charge it but it won't let me.

Welcome to the Community, @hondaelectricjef. I’ll help you with taking off taxes from an invoice in QuickBooks Online (QBO).

To help you with taking off sales taxes, you can set the items as non-taxable.

Let me show you how:

1.  Go to the Gear icon at the top.
2. Select Products and services.
3. Edit the item in question and make sure that the Sales tax category drop-down is Nontaxable. 
4. Click Save.

If you have already created the items, you can untick the tax box to remove sales tax when creating an invoice. You can refer to the screenshot below.

Furthermore, you can check out this article for more details regarding using automated sales tax on an invoice or sales receipt.

Feel free to visit our Sales tax page for more insights about managing your sales tax in QuickBooks.

Let me know if you need further assistance with taxes. The Community always has your back. Have a great day!