Thank you for discussing the detailed information of your concern, @jandt.
I'll provide some information and troubleshooting steps on how to resolve the sales tax that is defaulting back to our business address.
There are only several more things we'll need to prepare to make this resolve. First, we'll need to set up the Tax Agency for your customer's location:
- Go to Taxes in the left navigation menu.
- Select Sales tax settings.
- Click the Add agency button.
- Enter the correct Agency, Filing Frequency, and Start date.
- Tab Save.
Once done, make sure that the shipping address is entered in your customer's profile is correct.
Here's how:
- Click Sales on the left navigation menu, then choose the Customers tab.
- Select the customer name, then hit the Edit button.
- In the Address tab, enter the correct details in the fields for the shipping address.
- If you entered a Billing address, and it's the same as the shipping address, then check the Same as billing address check box.
- Tap Save.
After that, let's create a sample invoice to if the address is functioning well. Then click the See the math link perpendicular to Sales tax. See the sample screenshot below.


Otherwise, I recommend following more troubleshooting options through this link: Default customer sales tax rate in QBO.
Additionally, for more information about how to set up and use sales tax and how to apply it on your transactions, just in case.
Let me know if you have any queries. I'm happy to assist. Keep safe!