Problem
The user receives the "You must specify a Sales Tax Item for Tax zone" error and cannot export. This error is most often encountered when a customer does have tax zones set up in ServiceTitan or, has not designated a tax zone on an invoice for a variety of reasons.
Solution
First, create the tax zone in ServiceTitan. Then, create the liability account in Quickbooks.
Create the Tax Zone in ServiceTitan
In ServiceTitan, go to the navigation bar and click Settings. In the side panel, click Invoicing > Tax Zones.
Click Add Tax Zone.

In the Sales Tax Item field enter "ST Sales Tax".
Note: Make sure to spell this exactly.

Click Save.
Create the liability account in Quickbooks
In QuickBooks, create a new GL Account with the type Other Current Liability and name it Sales Tax Payable - ST:
Under Your Company, pick Chart of Accounts.

Click New.

Click Other Account Type > Other Current Liability.

Name the account "Sales Tax Payable - ST" > click Save & Close.

Add an Item type Service with the name ST Sales Tax.
Click Items & Services > New.

Map to newly created GL account Sales Tax Payable - ST.

Set the Account of the item as Sales Tax Payable - ST.

Click OK.
Return to the Accounting Tab in ServiceTitan > enter the batch number in the search field > Click on Batched > Right Click anywhere on the screen > Click Reload (this will hard refresh the page) > Re-export the Batch.