It's nice to see you posting here in the Community forum, Tony.
I'd be glad to assist you with tracking sales tax to invoices in QuickBooks Self-Employed (QBSE).
At this time, adding auto sales tax to invoices isn't an option in QBSE. In the meantime, you'll have to add it manually every time you collect sales tax.
To add sales tax to invoices, here's how:
In the left menu, click Invoices.
Click the Create invoice button.
Choose Add product or service.
Select the Product or Service dropdown and then choose + Add new.
Feel free to reach out to me if you have any more concerns or follow-up questions regarding managing invoices in QBSE. I'm here to provide further assistance.