Thank you for providing a well-detailed explanation about the calculation of Sales tax not based on your client's billing address, Justine. Turning off the Shipping button in Settings is not the option to calculate the Sales tax based on the billing address of your client. I'll provide you an explanation with this.
With this case, QBO will not calculate sales tax based on your customer's billing address. If there is no Shipping address turned on or entered in the customer's profile. QBO Automatically calculate the sales tax based on the location of the sale which is your business address.
Please refer to this article to learn more about adding the shipping addresses of your customer: Add a customer’s shipping address to invoices in QuickBooks Online.
After all of this is through, you can receive a payment from your customers if they already paid for your products.
These will help you to have the Sales tax calculation will be based on the billing address of your customer. If you encounter any issues or have additional questions, please hit the Reply button to assist you promptly.
