The harmonized sales tax (HST) is a Canadian tax that's in effect in half of the ten provinces (New Brunswick, Newfoundland and Labrador, Nova Scotia, Ontario, and Prince Edward Island).
It’s called a “harmonized” consumption tax, since it’s the federal goods and services tax (which is the same across provinces) combined with the provincial rate (which differs across provinces, like states in the U.S.). Each province that uses the HST has the same federal rate, but its own provincial rate, making each total HST rate different.
While studies showed (or estimated) that the HST would not negatively affect consumer spending, polls showed upwards of three quarters of Canadians said “eh, sorry, don’t like it very much.” TBD on the future of HST.