On each registration fee element, you’ll see the option to Charge Tax on this Fee. When a registrant selects a fee where this option has been selected, they will be charged tax on that amount. The tax will be added to their total registration fee during the checkout process.
In order for this option to actually do anything, however, you will need to set a Tax Rate in the Payment Settings section of the registration form:
When you have taxable fees included on your registration form, you will see a separate “Tax” line below the subtotal of each cart, and a “Total Tax Collected” line at the bottom of your registration summary reports.