Hello info177,
QuickBooks Online is designed to save you time. I'll help you change the default tax code so you're able to optimize the efficiency of your QuickBooks account.
At this time, you're unable to create a default tax code for all of your customers without editing their tax status individually. I can appreciate how convenient this would be, and I'd be happy to pass along your feedback to the software development team.
In the meantime, here's how to edit each customer's tax information:
1. Click Sales on the left navigation menu.
2. Select Customers at the top of the page.
3. Choose a customer from the list, and click Edit.
4. Select the Tax info tab.
5. Check the box next to Assign default tax code.
6. Select Exempt from the drop-down menu.
That's all there is to it. Each time you create an Estimate for your customer, the Tax Code will default to Exempt. If there's anything else I can help you with, please don't hesitate to reach out in the comments below.
Have a great day!