As of July 1st 2010, no company in Ontario will be tax exempt.
Customers in provinces that participate in HST will be charged their respective rates:
New Brunswick – 15%
Newfoundland & Labrador – 15%
Nova Scotia – 15%
Ontario – 13%
Prince Edward Island – 15%
Customers in provinces that do not participate in HST will only be charged 5% GST – Alberta, BC, Manitoba, Quebec, Northwest Territories, Nunavut, Saskatchewan & Yukon.