Change of Use on Commercial Property: The HST Bill for a Sale That Never Happened
You recovered the HST when you bought your commercial property. Move into it, turn it into apartments, or cancel your GST number, and the CRA treats it as if you sold it to yourself at market value. Here is the tax nobody sees coming.
I claimed the HST back when I bought my commercial property. If I later use it myself or rent it out and never actually sell it, why would I still owe HST?
Because the CRA treats a change of use as a deemed sale. Under CRA GST/HST Memorandum 19.4.2 (Commercial Real Property — Deemed Supplies) and the Excise Tax Act (ETA) sections 206 and 207, once you have recovered the HST on a commercial property as an input tax credit (ITC), moving that property out of commercial activity — into personal use or an exempt use — makes the CRA treat you as if you sold it at fair market value and immediately bought it back. You must self-assess and remit HST on that phantom sale, even though no money changed hands. A drop of 10% or more in commercial use triggers an adjustment; for an individual, crossing into more-than-50% personal use is treated as a full exit from commercial use. The amount is capped at the property basic tax content.
Source: CRA — GST/HST Memorandum 19.4.2 (Commercial Real Property — Deemed Supplies) and Excise Tax Act ss. 206–207 (canada.ca / laws-lois.justice.gc.ca, accessed July 2026)
I am Arthur Zhao. The HST that ambushes commercial property owners rarely shows up on a closing statement — it shows up when nothing appears to happen at all.
Picture a physiotherapist who bought her clinic unit years ago, ran her practice out of it, and recovered the full HST on the purchase as an input tax credit. She winds the practice down and turns the unit into her own studio apartment. No buyer, no closing, no cheque. A few months later her accountant tells her she owes the CRA a five-figure HST bill.
That bill is not a penalty. It is a deemed supply — the CRA reasoning that she only got the credit because the property was used commercially, and now that the commercial use is gone, so is the basis for the credit. This article walks through what sets it off, how big it gets, how it differs from an actual sale, and the one thing almost everyone confuses it with — the income-tax rule that shares the same idea but is a completely separate tax.
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The rule in one line: a sale with no buyer
The Excise Tax Act contains a set of deemed supply rules. When real property crosses certain lines of use, the CRA pretends you sold it to yourself at fair market value (FMV) and bought it straight back. That imaginary sale generates HST you have to account for.
Why build it this way? Because the only reason you could claim the purchase HST back as an input tax credit (ITC) was that the property served a commercial activity. Take the property out of commercial activity and the justification for that credit disappears — so the system claws it back by deeming a sale.
The mental model that keeps you out of trouble: a deemed supply is not new tax out of thin air; it is the CRA settling up the credit you already took.
ℹ️This article deals with capital real property — property you hold to use or to earn rent. If the real estate is inventory you hold to flip, a different set of rules applies.
First question: did you ever recover the HST?
If you bought from a non-registrant, or never recovered the HST because the use was exempt, most of the deemed-supply machinery simply never fires — there is no credit to claw back. The trap is built for owners who did recover the tax.
That is why the danger runs highest for property bought as a going commercial concern: offices, clinics, retail units, warehouses — the ones where an accountant recovered a large ITC on day one. The bigger the credit you took, the bigger the settling-up when the use changes.
The 10% line and the 50% cliff
According to CRA (GST/HST Memorandum 19.4.2) and ETA section 206, for most registrants a drop of 10% or more in commercial use triggers a deemed sale of the portion that changed — a partial settling-up, proportional to the decrease.
For an individual, ETA section 207 adds a sharper edge. The moment the property becomes used primarily — more than 50% — for that individual’s (or a related individual’s) personal use and enjoyment, it is treated as a full exit from commercial use, even if the shift itself was only a few percent. You do not settle up on the small change; you settle up on the whole property.
Convert it to apartments and it becomes a self-supply
Under CRA GST/HST Memorandum 19.2.3 (Residential Real Property — Deemed Supplies) and ETA section 191, when a builder gives possession of a newly built or substantially renovated (90% or more of the interior removed or replaced) residential unit to its first occupant under a lease — or moves in themselves — they are deemed to have sold the whole unit at fair market value and bought it back, and must self-assess HST on that value.
The reason it bites so reliably: long-term residential rent is an exempt supply. The landlord charges no HST on the rent and can therefore never recover the embedded tax through future rent. Section 191 forces the reckoning at the moment the property flips to residential rental — which is why “commercial to residential rental” almost always produces an HST bill.
⚠️Before you convert commercial space to long-term residential rental, model the self-supply. Under ETA section 191, the flip to residential rental deems a sale at fair market value and an HST bill that no rent cheque will ever reimburse.
💡 The myth worth killing: leasing your commercial unit out commercially does not trigger a deemed supply. Renting commercial space to a commercial tenant — collecting rent and charging HST on it — is itself a commercial activity, so the basis for your ITC survives. The danger is not renting; it is the kind of renting. Commercial lease: safe. Residential lease: a self-supply waiting to happen.
Cancelling your GST/HST number — the quiet trigger
Under ETA section 171(3), when a person stops being a GST/HST registrant, they are deemed — in the instant before the number is cancelled — to have stopped using their capital real property in commercial activity. That deems a sale at fair market value, and the tax has to be self-assessed.
The classic story: an owner retires, closes the business, and cancels the GST number as a tidy-up step — forgetting the commercial property still on the books that carried a large ITC years ago. Cancelling the number is itself the detonator.
One nuance worth carrying: a “registrant” includes a person who is required to be registered, so a premature or mistaken cancellation does not automatically force the deemed sale. But that is expert-judgment territory — do not treat it as a planning tool.
The size of the bill: basic tax content
Under ETA section 123(1), basic tax content is, roughly, the GST/HST you actually paid on the last acquisition and on any improvements, minus amounts recoverable by rebate (but not by ITCs), reduced for any decline in the property’s fair market value. In plain terms: the tax still embedded in the property that you have not yet given back, capped at the tax on its current value.
Ontario’s HST rate is 13% (per CRA), so on a commercial property worth a few million dollars the deemed supply routinely lands in six figures. That size is exactly why the number belongs in your planning before you change the use, not in a surprise assessment after.
🚨The deemed-supply tax turns on fair market value, and FMV comes from an appraisal, not a guess. Get an independent valuation before you change the use — it drives how much you owe and is your evidence if the CRA reviews the file.
This is not the income-tax change-of-use rule (ITA s.45)
The Income Tax Act (ITA) section 45 also has a change-of-use rule — but it governs capital gains. When use changes, the property is deemed disposed of at market value, potentially realising a taxable gain reported on your income-tax return.
The ETA rules in this article (sections 206, 207 and 191) govern HST, reported on your GST/HST return.
A single change of use can hit both at once: income tax settles the gain, HST settles the credit. Two taxes, two returns, two calculations — never reason about one using the rules of the other.
A playbook for owners and their agents
1. Did you ever claim ITCs? If not, much of the deemed-supply exposure never arises. If you did, take the calculation seriously.
2. Does the new use stay inside commercial activity? Commercial lease: safe. Personal use, residential rental, exempt use: dangerous.
3. Did the change cross a threshold? Non-individuals watch the 10% line; individuals also watch the 50% primary-use cliff.
4. Did anyone cancel the GST number? With property still on the books, deregistration is itself a trigger.
None of this replaces professional advice — with a self-assessment in the six figures, bring in an accountant or commodity-tax adviser before the use changes, backed by a defensible valuation. The value an agent adds is raising this question before the client signs or converts — not cleaning up afterward.
✅The one-line takeaway: if you ever recovered the HST, any move that takes the property out of commercial use — living in it, renting it residentially, or deregistering — can produce a tax you never actually collected. Run the numbers before you change the use, not after.
Frequently Asked Questions
If I lease my commercial unit to another business, do I owe HST on the change?
Generally no. Leasing commercial space to a commercial tenant is itself a commercial activity, so the property never leaves commercial use and the basis for your input tax credit survives. The deemed supply fires when the use leaves commercial activity — for example, moving in yourself or converting to long-term residential rental.
How much does commercial use have to fall before I owe anything?
According to CRA (GST/HST Memorandum 19.4.2) and ETA section 206, for most registrants a drop of 10% or more in commercial use triggers a proportional deemed sale. If the owner is an individual, ETA section 207 treats any shift into more-than-50% personal use as a full exit from commercial use, even if the change itself is under 10%.
Is the deemed-sale tax based on what I paid or on today’s value?
It is capped by the property’s basic tax content (ETA section 123(1)) — broadly, the GST/HST you paid on the purchase and improvements that you have not already recovered by rebate, limited to the tax on the property’s current fair market value. It is neither a simple re-run of your original price nor an unlimited recharge on today’s value.
I only cancelled my GST/HST number and kept the property. Do I still owe tax?
You might. Under ETA section 171(3), when you stop being a registrant you are deemed to stop using your capital real property commercially in the instant before cancellation, which triggers a deemed sale at fair market value. Inventory your commercial holdings that carried an ITC before you cancel the number.
Is this the same as the income-tax change-of-use rule?
No. ITA section 45 governs capital gains on your income-tax return; the HST deemed supply in this article governs the claw-back of input tax credits on your GST/HST return. One change of use can trigger both, but they are two separate taxes on two different returns.
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