Does HST apply differently to a brand-new commercial building versus an older used one in Ontario?

Not in the way many buyers expect from residential real estate. With homes, age is the key dividing line — a new or substantially renovated home generally attracts HST, while a resale used home is typically exempt. Commercial real property doesn't follow that same pattern: a sale by a GST/HST registrant in the course of a commercial activity is generally taxable whether the building was constructed last year or decades ago.

This means a buyer can't assume an older, previously used commercial building will be HST-exempt the way an older house often is. What actually determines the HST treatment is the seller's registration status and whether the sale happens in the course of a commercial activity, not the building's age or how many times it's changed hands. There can be exceptions and nuances depending on the specific facts of a sale, which is exactly why this shouldn't be assumed either way without confirming it.

Because getting this wrong can mean an unexpected tax bill or a missed self-assessment obligation, buyers and their advisors should confirm the applicable HST treatment for the specific building and transaction structure before finalizing price and closing arrangements, rather than relying on assumptions carried over from residential deals.