To ensure accurate reporting on tax liability, we strongly recommend allowing ServiceTitan to calculate the tax field on invoices. If the tax field is calculated incorrectly, we do not recommend manually updating the tax on an invoice. Instead, correct your tax setup so that ServiceTitan calculates the intended amount. This article will help you understand how to update the tax zone of a location, and ensure all open invoices are updated to the new tax zone if necessary.
Workflows
Apply new tax zone to all locations
These are the steps for updating the tax zone on a single invoice:
Make sure the invoice is in Pending status. If the invoice is Posted, unpost the invoice.
Note: If the invoice is Exported, follow these steps.
Click Update Invoice Details.

Click Tax Zone.

Select the correct tax zone from the dropdown.

On the invoice, click the refresh button next to the tax field to recalculate the tax based on the current tax zone set on the location.
Note: Account configuration is required to enable this feature.
Repeat steps 1 and 5 for all other open invoices for the location.
Note: Remember to repost any invoices you unposted.
Caution: Update the tax zone of the location, so you don't have to manually update invoices in the future.
Note: You can also change the tax zone on the invoice, save, and then change it back to the original tax zone to resolve the issue. Set tax zone doesn't retroactively apply a tax zone to open invoices.