People usually arrive at this question from one of two directions.
Either they’ve spent a great deal of money on a renovation and want to know whether they can claim a rebate. Or they’re partway through gutting a house and someone has mentioned that they might be able to.
The test is stricter than most people hope in one respect, and considerably more generous than most people expect in another.
It isn’t about what you spent
Start here, because it’s where the confusion lives.
“Substantial renovation” sounds like it should mean a substantial amount of money. It doesn’t. The test measures how much of the existing interior was removed or replaced — not the invoice total.
This produces two results that feel wrong until you understand the rule.
A very expensive renovation can fail. A $400,000 project that produced an extraordinary kitchen, three new bathrooms and a finished basement, while leaving most of the interior in place, may not qualify at all.
A more modest one can succeed. Stripping a small house back throughout, on a considerably smaller budget, may qualify comfortably.
The bar: back to the studs
The legislation says substantially all of the interior of the existing building must have been removed or replaced. In practice that’s treated as around 90%.
The plain-language version we use: the house has to have been taken back to the studs. But there are always exceptions.
That’s a demanding standard, and it’s worth being honest about it. Not all renovations — even large, expensive, disruptive ones — meet the standard. If you replaced the kitchen, did the bathrooms, refinished the floors and repainted throughout, that is a major renovation and it is almost certainly not a substantial one.
What qualifies is the project where the interior came out. Partition walls down, finishes gone, mechanical systems stripped, the inside of the building reduced to its frame and rebuilt.
What you don’t have to touch
Here’s where it’s more generous than people assume.
The following do not need to be impacted for a substantial rebate to qualify:
- The foundation
- The exterior walls
- Interior supporting walls
- The floors
- The roof
- The staircases
You don’t have to demolish the house or replace its structure. The test is about the interior that came out, not the shell that stayed.
So a house that is visibly still standing, still on its original foundation, under its original roof, can absolutely qualify — provided the inside genuinely went.
How is the 90% actually measured?
There’s no formula. The CRA doesn’t prescribe a method, and it’s a question of fact judged on the particular building.
Which means a claim has to be documented rather than asserted. A figure arrived at by feel won’t survive a review. A room-by-room account of what came out, supported by photographs and itemized invoices, will stand up considerably better.
This is why the advice further down this page — photograph everything — matters more than it sounds like it should.
What about an addition?
An addition, on its own, is not a substantial renovation. Doubling the size of your kitchen doesn’t qualify however comprehensive the work.
There is a separate route where the work is extensive enough that what results is effectively a new home. The requirement there is that the addition doubles the floor space of the existing house. Not increases it substantially — doubles it.
That’s a high bar and most additions don’t come close. A second storey on a bungalow might. An extension off the back almost certainly doesn’t.
If your project is mostly an addition, the honest answer is that it probably doesn’t qualify on that basis. If it’s an addition alongside a full interior strip, the renovation is what carries the claim — and, as above, the addition then forms part of what you can claim on.
Converting a commercial building
Worth stating plainly, because it surprises people: converting a non-residential building into a home qualifies. A commercial unit, a warehouse, an office turned into a residence is treated as new housing for rebate purposes.
The conversion route doesn’t turn on the 90% interior test in the same way, because the building wasn’t residential to begin with.
Why this matters more than it used to
Until recently, a successful substantial renovation claim in Ontario recovered a maximum of $24,000 provincially.
That’s no longer the ceiling. A substantially renovated home qualifies for Ontario’s enhanced rebate, which means the amount at stake on these claims is now several times what it was.
The work involved in documenting one hasn’t changed. What’s recoverable has — and by enough that projects previously dismissed as not worth the paperwork are worth reconsidering.
If you’re renovating right now, do these two things
The most useful advice on this page, and it costs nothing.
Photograph everything, especially mid-demolition. Once the drywall is back up, proving what was behind it becomes extremely difficult. Empty rooms, stripped walls, exposed studs — five minutes at each stage with a phone camera. Given that the 90% question is judged on evidence rather than calculated by formula, those photographs may be the whole claim.
Ask your contractors for itemised invoices, not lump sums. “Renovation work — $85,000” is nearly useless. A breakdown showing materials, labour and GST/HST paid is what a claim is built from. Contractors will generally provide it if you ask at the outset. Asking eighteen months later is a harder conversation.
Neither costs you anything today. Both decide what’s possible later.
If your claim was denied
Substantial renovation denials are among the more challengeable decisions the CRA makes, precisely because they turn on a judgement about scope rather than a clear-cut fact.
You have 90 days from the date on your notice of assessment to file a Notice of Objection. That deadline is firm.
If the denial rested on a view about how much of the interior was replaced, and you have photographs and invoices telling a different story, that’s an argument worth making.
The short version
The test is how much of the interior came out, not how much you spent. The working standard is back to the studs.
The structure — foundation, walls, floors, roof, stairs — doesn’t count against you and can all stay.
And once you qualify, the whole project goes into the claim, including the structural work and any addition.
If you’re in the middle of the work right now: photograph everything, and get itemised invoices.