Overview of Taxation
Sales Tax settings are located on the "Basics" page in "Setup". Scroll to the bottom of the page and click "Advance Settings" to make changes.
Sales tax on services: controls how much tax is added to every sale. If tax is greater than 0%, boomtime defaults to charging tax on service-based GCs only. If you desire to charge tax on dollar-based GCs as well, then you need to make sure the Tax dollar amount GCs? checkbox is checked.
You should consult with your tax professional to decide whether, and how, to charge tax for your jurisdiction. Your tax professional can also help you understand when a taxable event occurs, not just for when to charge customers for tax, but when to pay the tax (i.e. after redemption and/or recognizing revenues after the expiration date hits).
Note that in the United States, there are very few jurisdictions where GCs should be taxed. Usually only those jurisdictions who charge Gross Receipts Tax for services will require tax on service-based GCs. boomtime has not yet seen a jurisdiction require taxation on dollar-based GCs.
The litmus test is: Has a taxable event occurred? In GC sales, the taxable event usually occurs when a service is sold or performed. Usually, this means, when someone purchases a service-based GC, or has redeemed a dollar-based GC. A taxable event also (usually) occurs when an unredeemed GC expires.
Please consult with your tax professional to clear up any particular taxation issues or questions you may have.