Does a residential condo unit built above ground-floor retail get the same HST treatment as a standalone home?

Largely, yes, for the residential unit itself. A new residential condominium unit is generally subject to the same HST new-housing rules whether it sits above ground-floor retail in a mixed-use building or stands entirely on its own, provided it genuinely qualifies as a residential complex under the applicable rules. The same general HST and rebate mechanisms that apply to a standalone new home purchase can apply to that unit.

What's different is the building as a whole, not the residential unit's own treatment. The ground-floor retail or commercial space in the same building is assessed under ordinary commercial real property HST rules, which work differently than the residential new-housing rules. Commercial space doesn't get the same rebate treatment a new home purchase might, and is generally taxable based on its own commercial-activity rules rather than residential ones. So while your specific condo unit is treated much like a standalone new home for HST purposes, the building isn't taxed uniformly overall.

Given how specific and changeable current HST rebate rules and figures can be, buyers of a new residential unit in a mixed-use building should confirm the current rebate eligibility and treatment with their lawyer or accountant rather than assuming figures from a standalone home purchase apply automatically.