Yes. In Ontario you pay 13% HST on the real estate commission, and the tax is added on top of the rate you agree to rather than built into it. If a home sells for $900,000 and the commission is 5%, that commission is $45,000, and the HST adds a further $5,850, for a total of $50,850 at closing.
The seller normally pays the full commission out of the sale proceeds, so the seller also carries the HST on it. Both amounts come off the top of the sale price before the remaining funds reach you. The money changes hands on closing day, and your real estate lawyer deducts the brokerage's invoice, tax included, from what the buyer's side sends over.
Commission rates are not fixed by law. They are negotiated between you and your brokerage and written into the listing agreement you sign before the property goes on the market. Whatever rate you settle on, the 13% HST applies to it, because the brokerage is providing a taxable service. That holds true whether the fee is a flat amount or a percentage, and whether one brokerage or two end up sharing it. For a fuller picture of how that fee is structured and split, see how real estate agents get paid in Ontario.
When you budget for a sale, treat the commission and its HST as a single line. A quoted 5% works out closer to 5.65% of the sale price once the tax is included, and on a Toronto-priced home that gap is real money. HST on the commission is only one of several costs a seller carries, alongside legal fees, a possible mortgage discharge, and getting the home ready to show.
Related reading: How Do Real Estate Agents Get Paid in Ontario?, What Is a Listing Agreement in Ontario?, and What Are the Costs of Selling a Condo in Toronto?
