When you create any event or appointment in the Servv, it creates a product in the Shopify in order to support the checkout process. You can always go to the product created in the Shopify and make changes in the checkout process.
To remove tax option from the Events or Appointments please follow the steps below:
In the Servv, go to Events or Appointments page. Next, go to the event/appointment you want to edit and click on "View Product Details" option in the right side of the event/appointment.
Or, go to Shopify Products > All Products and look for the product with the Event name that you created.
As you scroll down the product options, you will see a Pricing section. Uncheck the "Charge tax on this product" option and Save.
You will see that tax will be removed from your events/appointments.
Similarly, you can make other changes to the product associated with checkout.