To apply tax on your surcharges:

Step 1: Visit Setup > Location Setup.
Step 2: Select the appropriate location.
Step 3: Click on Menu Management > Tax Rates and add a tax rate.
Step 4: From Location Setup, visit Menu Management > Surcharges and Discounts.
Step 5: Edit the surcharge you want to add tax on, select the Taxable option, and click on the appropriate rate.
Step 6: Click Save.

Watch our video guide on Adding and Applying a Surcharge: