In Absorb, we have the ability to set tax rates at both the Country and State/Province level as a percentage on the final price as seen on the payment gateway payment page. Tax rates can be set by any Absorb representative, and by opening a support ticket at either https://support.absorblms.com, or by emailing firstname.lastname@example.org directly we would be happy to set this information as needed.
Logged In Users
When logged in users make a purchase, any tax rates that apply to the users assigned country and/or state/province will be applied upon checkout. The final tax value will appear on the payment gateway page, and be included in the final price of the purchase. If a user does not have a country and/or province/state configured, they will be prompted to enter this info prior to being redirected to the payment gateway, in order to establish whether or not tax should be applied.
Non-Logged In Users
Non-logged in users will have much the same experience as logged in users, where the country/state/province information entered during the user sign up process will be used to calculate any required taxes.
Note: In both cases (logged or non-logged in), the country and province/state that are set in the Absorb user/profile is used to calculate taxes, and not the billing address entered on the payment gateway page.