What is a change of use?

A change of use happens when a property that was held for one purpose starts being held for another. The common case: a client moves out of their home and rents it. The property was personal-use property; now it earns income. It can also run the other way, where a former rental becomes the client's residence, and it can be partial, such as converting part of a house to a rental unit.

Under subsection 45(1), a change of use is a deemed disposition at fair market value. The client is treated as having sold the property at its current value and immediately reacquired it at that same value. The reacquisition steps up the cost base, which sounds helpful, but the deemed sale realizes the accrued gain in the meantime. Where the property was the client's principal residence up to that point, the gain can be sheltered by the principal residence exemption on this change of use. The catch is that the client has now crystallized a disposition they may not have wanted, started a new holding period at the stepped-up cost, and, on a conversion to income use, only 50% of the gain is added to the cost for capital cost allowance purposes even though the full amount was recognized.

What does the 45(2) election do?

Subsection 45(2) lets the taxpayer elect that no change of use has occurred when a personal-use property begins to be used to earn income. The deemed disposition under 45(1) is switched off. The cost base stays where it was, no gain is realized on the conversion, and, most usefully, the property can continue to be designated as a principal residence for up to four additional taxation years, even though the client no longer lives there and even if it is being rented out. There is no requirement to ordinarily inhabit the property during those years. The only condition on the four-year extension is that no other property is designated as the principal residence for those same years.

The election is made by attaching a letter to the return for the year the use changes. It applies even where the property is rented and generating income: the client reports the rental income as normal, and the election only concerns the capital treatment of the property itself.

This election is frequently advantageous and just as frequently overlooked. Missing it is one of the most common principal residence exemption change of use errors in practice: the change of use goes unnoticed, no election is filed, a capital gain is deemed to arise, and often it is never even reported.

The two conditions, and why one of them is a trap

The election carries two conditions. The first is straightforward. The second is where practitioners lose the election without realizing it.

Condition one: no other property designated as principal residence

The four-year extension only works if the client isn't claiming the exemption on a second property for the overlapping years. If the client buys a new home and designates it, they cannot also run the 45(2) four-year designation on the old one for the same years. The years are a finite resource, spent on one property or the other.

Condition two: no CCA, and claiming it is a landmine, not a checkbox

Every thin online guide lists "no capital cost allowance" as a condition and moves on. What they never explain is the mechanism, or the timing of the damage. If capital cost allowance is claimed on the property in a year after the change of use, CRA's administrative position is that the 45(2) election CCA claim is treated as rescinding the election on the first day of the taxation year in which the CCA is claimed. That is not a soft consequence. Rescission fires the very 45(1) deemed disposition the election was filed to prevent, deemed to occur on January 1 of the CCA-claim year, at the property's fair market value on that date. The client is pushed into the deemed sale, with the gain, reacquisition, and fresh holding period, as of that day.

Note the narrow carve-out on partial changes of use. Where the income use is incidental, such as renting a room or keeping a home office, CRA's administrative position is that no change of use arises provided no CCA is taken. You can still claim CCA on the furniture, a fridge, or a stove without jeopardizing the residence, because those are separate assets from the housing unit. Claim CCA on a portion of the house itself, and that portion stops qualifying as principal residence and a change of use applies to it.

A worked example: the numbers, and why timing changes the answer

Competitors' guides contain no numbers. Here is the arithmetic on a single fact pattern, run two ways, because the timing of what you do with the election drives the result.

The facts. Candice buys a home in Year 1 for $100,000. It is her principal residence until Year 8, when she moves out and rents it. The house is worth $150,000 at that point, and she files a 45(2) election. In Year 15 she sells for $300,000. Along the way, the house was worth $290,000 in Year 13.

Scenario A: election filed and never revoked

The 45(2) election means no deemed disposition in Year 8; the whole period is treated as continuous ownership. On the Year 15 sale:

The property qualifies as principal residence for 12 years: the 8 years she lived there, plus the 4 bonus years the election buys (8 + 4). She owned it for 15 years. Applying the exemption formula with the one-plus rule:

Scenario B: election revoked in Year 13

A 45(2) election can be rescinded, and rescission triggers a deemed disposition on the first day of the year of rescission. Rescind in Year 13, and Candice is deemed to dispose of the house on January 1 of Year 13 at its then-value of $290,000:

The entire $190,000 gain to Year 13 is sheltered: 13 designated years (8 + 4 + the one-plus) over 13 years of ownership is 100%. She reacquires at $290,000. On the actual Year 15 sale:

Revoking in Year 13 leaves Candice with a $10,000 gain versus $26,667 if she rode the election to the end. The reason is entirely mechanical: the deemed disposition on rescission lets her capture the appreciation up to Year 13 inside a 100%-exempt fraction, and start a fresh, higher cost base for the small remaining run-up. The lesson is that the election is not "set and forget." A rescission timed to a high-value year can beat holding the election, and you only see the opportunity if you re-run the numbers before the final sale. It is also worth seeing the connection to the CCA trap above: an inadvertent CCA claim forces this same deemed-disposition-on-January-1 mechanic on you in a year you did not choose. The difference between a planning tool and an accident is entirely which year the clock stops.

How this all connects

Practitioners get burned when they treat these provisions as separate switches instead of one interlocking system. Here is the mental map.

45(1) → 45(2) → the PRE formula

A change of use is a 45(1) deemed disposition. The 45(2) election suspends it and, through the four-year designation, feeds directly into the principal residence exemption formula:

Exempt portion of gain = (1 + years designated as principal residence) / years owned

That leading "1" is the one-plus rule. It exists to cover the year a client sells one home and buys another, letting a single year of overlap be fully covered rather than pro-rated. Two cautions the slides stress: the one-plus is only available if the taxpayer was resident in Canada in the year the property was acquired (it does not rescue a property bought while non-resident), and a year the client was non-resident cannot be designated. Vacant land or a house under construction can't be a designated year either, though those years still sit in the denominator, and the one-plus can still apply.

45(2) and 45(3): the mirror image

Subsection 45(3) is the counterpart running the other direction, an income-use property that becomes a principal residence. Same problem (a 45(1)-type deemed disposition and reacquisition at FMV on conversion), same style of relief, but the conditions differ. Under the s.45(3) election the property must actually become a principal residence at the time of the change; no CCA can have been claimed on the building after 1984 (the same CCA landmine, phrased for the reverse direction); and the election is made in the year of ultimate disposition, though it is cleaner to file it by letter for the year of conversion. As with 45(2), a resumption of occupancy after a 45(2) election is not itself a second change of use, so moving back in doesn't restart the analysis.

The four-year designation and its extension

The four extra years under 45(2) can stretch beyond four, indefinitely, where the reason for the change of use is a work relocation and the client eventually moves back into the property (or dies still owning it). This is the provision to reach for when a client is posted elsewhere for work and keeps the family home.

When not to elect

The election isn't automatically right. It shines when there's no other property to designate (and you can always rescind later if the property drops in value), or when the per-year gain on the existing residence will outrun the per-year gain on the new one. It's weak when the client has owned the existing residence for many years and it isn't expected to appreciate much more, because the pro-ration of the few non-qualifying years is trivial. Suppose a residence owned for 40 years is sold four years after the change of use with no election: roughly 3/44 of the gain is taxable. That's a rounding error, and locking up the designation may cost more than it saves on the client's other property.

The flipping rule sits on top of all of it

None of the above matters if the disposition is caught by the residential property flipping rule (see next section), which converts the gain to business income and denies the exemption outright, regardless of any election.

Traps and common errors

The CCA landmine (covered above) is the big one. Claiming building CCA in a year after the change of use rescinds a 45(2) election as of January 1 of that year and fires the deemed disposition. Guard the file against it, because the disposition happens the moment the claim is made. There is no clean undo.

The flipping rule can override the exemption entirely. The residential property flipping rule applies to dispositions on or after January 1, 2023 and is fully in force for the current year. If a "flipped property" (a housing unit, or a right to acquire one, located in Canada) is held for less than 365 consecutive days before disposition, the profit is deemed to be business income, not a capital gain, and the property is not capital property. Because both the principal residence exemption and a 45(2) election require capital property, both are simply unavailable. The rule deems a gain to business income but does not deem a loss to be a business loss. It applies only to residential real estate situated in Canada, and curiously not to foreign property. Assigning a purchase agreement can never qualify for the exemption regardless, because an agreement to buy is not a housing unit and is not ordinarily inhabited.

The definition carves out dispositions that can reasonably be considered to occur because of, or in anticipation of, an enumerated life event: the death of the taxpayer or a related person; an addition to the household (birth, adoption, an elderly relative moving in); a marriage or common-law breakdown where the taxpayer has lived separate and apart at least 90 days before the disposition; a threat to the personal safety of the taxpayer or a related person; a serious illness or disability of the taxpayer or a related person; an eligible relocation (one bringing the taxpayer or spouse at least 40 kilometres closer to a new work or school location); an involuntary termination of the taxpayer's or spouse's employment; the taxpayer's insolvency; or the destruction or expropriation of the property. The objective triggers are easy to substantiate. For the subjective ones, such as a safety threat, illness or disability, or eligible relocation, CRA expects supporting documentation such as medical certificates, termination letters, or separation agreements, so tell the client to keep it.

The dangerous part is where the flipping rule collides with change of use. Watch for: a change of use followed by a sale within 12 months; a change of use within 12 months; a change of use and then a second change back within 12 months; a rollover to a spouse, alter-ego, spousal or joint-spousal trust followed by a sale or distribution within 12 months; a transfer to a spouse followed by a sale within 12 months. Sequential dispositions, even tax-deferred rollovers, can set the 365-day clock running so that a later disposition trips the rule. Clients frequently discover the problem only after the fact, when it is too late to restructure.

Missing the election altogether. The single most common change-of-use error is simply failing to make a 45(2) election when it's appropriate. The home becomes a rental, no election is filed, a capital gain is deemed to arise, and it often goes unreported. Build a habit of asking about any change of address; it is frequently the only clue that a change of use (or a sale) happened.

Ignoring the four-year extension. Even where the election is made, practitioners forget that it buys four additional designation years (longer for a work relocation). Those years are free exemption if no other property is designated, so don't leave them on the table.

Rescission and late filing: get the mechanics right. A 45(2) election can be rescinded (or revoked) by sending a letter to CRA. When it is, a deemed disposition arises on the first day of the year of rescission, and as the worked example shows, that timing can be turned to the client's advantage in a high-value year. A 45(2) election that was missed can be late-filed under the taxpayer relief provisions (subsection 220(3.2)); the election letter goes to the client's tax centre with a formal request to late-file, and CRA has discretion to accept or reject it. The late-designation penalty, where a principal residence designation itself was missed, is the lesser of $8,000 or $100 for each complete month from the original filing due date to the date the amendment is filed in acceptable form. CRA can waive or cancel that penalty under Information Circular IC07-1R1, but only in the narrow taxpayer-relief circumstances: extraordinary events beyond the client's control, serious illness, or CRA's own error or delay. Simple oversight or not knowing the rule does not qualify, so don't promise a client the penalty will be forgiven.

The timing and sequencing questions practitioners actually ask