Donation disclaimer message checkbox available?

-- url of the page with the problem -- : apf.cloudaccess.net
-- HikaShop version -- : 2.4.0
-- Joomla version -- : 3.4.1
-- PHP version -- : 5.6.3

I am helping a friend build his site and he purchased the Essentials Hika Shop. Now it looks like we need to upgrade his account to Business since he wants to be able to take Donations. He is willing to upgrade but has one concern because he is NOT a tax-exempt entity.

He wants to know if there is some way for people to hopefully click on something to state that they know he is not tax exempt and that their donation will not be tax-deductible. Is this possible somehow?

Yes. You'll be able to create a custom field of the table "item" and of the type "checkbox" and configure it to the donation product(s) you're going to configure via the menu Display>Custom fields.
You can turn on the "required" option of the field so that the customers have to check the checkbox in order to proceed.