Tax Exempt status?

[steve@realm30.com]

HI! I'm new to EasyCart so maybe this feature already exists, I apologize if it does. My client is selling sheet music to teachers, many of which have tax exempt status. Is there a way to activate a checkbox on checkout that reads "I'm a tax exempt teacher" and a way for them to attach a PDF to the order (to upload a tax exempt certificate PDF file to my client)?