Alternative Minimum Tax in Canada: Who the Reformed AMT Actually Catches

The alternative minimum tax is a second, parallel calculation of your federal tax. You work out your tax the ordinary way, you work it out again under a set of less generous rules, and you pay whichever number is higher. The extra amount is reported on line 41700 and calculated on Form T691.

The AMT was rebuilt for tax years beginning after 2023, and the rebuild did something specific: it stopped catching middle-income people with modest tax preferences, and started catching a narrow group with large one-time events. If you have never thought about AMT, that is probably correct. If you are about to sell a business, donate appreciated shares, or exercise a large block of options, it is now the first thing to model.

What changed, and what it means in practice

Three parameters moved at once.

The exemption rose from $40,000 to the start of the fourth federal tax bracket, which put it above $173,000 for 2024 and it is indexed each year after that. Below the exemption there is no AMT at all, so the reform removed most ordinary taxpayers from the calculation entirely. The current amount is on the T691 form itself and should be read from there rather than remembered.

The rate rose from 15% to 20.5%. And the base broadened, which is where the damage actually happens.

The capital gains line is the one that decides most cases. Under ordinary rules, half of a capital gain is taxable. Under AMT, all of it is. That is a straight doubling of the income the AMT calculation sees.

It is worth being precise about the inclusion rate here, because a lot of material written in 2024 and 2025 is wrong. The proposed increase to a two-thirds inclusion rate was deferred in January 2025 and then cancelled outright on 21 March 2025. The regular inclusion rate is one-half. The gap between regular tax and AMT on a capital gain is therefore exactly two to one, and the increase in the lifetime capital gains exemption survived the cancellation. The broader mechanics are in the capital gains inclusion rate.

Who gets caught

AMT is a problem when a large amount of preferentially taxed income lands in a single year against a small amount of ordinary income. Four situations produce that shape.

Selling a qualified small business corporation and claiming the exemption. The exemption removes the gain from regular tax entirely. AMT still counts 30% of it. A vendor whose entire year consists of an exempt share sale can pay minimum tax on a transaction that produces no ordinary tax at all. This is the single most common AMT event in practice, and it is covered from the sale side in the capital gains exemption on small business shares.

Donating appreciated publicly listed securities. The regular rules are generous: no tax on the gain, plus a donation credit. Under AMT, 30% of the gain is included and only 80% of the credit is allowed. A large in-kind donation in a low-income year can create minimum tax. This does not make the donation a bad idea, and the treatment is discussed alongside the other mechanics in charitable giving and tax in Canada.

A large one-time capital gain. Selling a cottage, a rental property, or a concentrated investment position. Ordinary income for the year is low, the gain is enormous, and doubling it inside the AMT base clears the exemption easily.

Exercising employee stock options. The 50% deduction that makes option benefits attractive under ordinary rules does not exist in the AMT base. See employee stock option tax planning.

Will a single year contain a large capital gain, an
exempt share sale, an in-kind donation, or an option exercise?
├─ NO ──> AMT is very unlikely. Stop here.
└─ YES
   │
   Is your ordinary taxable income in that year already
   high, from salary or a business?
   ├─ YES ──> AMT is usually absorbed. Regular tax exceeds
   │          the minimum. Model it, but expect no AMT.
   └─ NO (a low-income year, or retirement)
      │
      Will you have substantial ordinary income in the
      NEXT seven years to recover the credit against?
      ├─ YES ──> AMT is a timing cost. Manage the cash,
      │          then reclaim it on line 40427.
      └─ NO ───> AMT is a PERMANENT cost. Restructure the
                 transaction before you sign anything.

The carryforward is what decides whether AMT hurts

Minimum tax is not a separate tax you simply lose. The excess you pay becomes a credit you can apply against ordinary tax in the following seven years, claimed on line 40427. The credit can only be used to the extent your regular tax exceeds your minimum tax in the recovery year.

That condition is the whole question. A 45-year-old who sells a business and then keeps working recovers the credit and has, in effect, made an interest-free loan to the government. A 68-year-old who sells a business and then retires on dividend income may never have a year where regular tax exceeds the minimum, and the AMT becomes permanent. Same transaction, entirely different cost.

So the useful diagnostic is not “will I trigger AMT” but “will I have seven years of ordinary income afterward”. Answer that before you decide whether AMT is worth planning around.

Ontario adds to the federal number

The 20.5% federal rate understates the cost for Ontario residents. Where Form T691 produces a minimum tax amount, Form ON428 carries an additional tax for minimum tax purposes calculated from the federal figure, and being subject to it also disqualifies you from the Ontario tax reduction. Model the combined number, not the federal one.

Planning that actually works

Spread the realisation. The exemption is annual. Two gains of half the size in two calendar years may both fall under the exemption where one large gain does not. This works for portfolio positions and for staged sales. It does not work for a single share sale that has to close on one day.

Match the year to your income. If a transaction is discretionary, prefer a year in which you already have substantial ordinary income. The regular tax absorbs the minimum, and no AMT arises.

Time donations against income, not against the calendar. An in-kind donation in a year with high employment income is efficient. The same donation in the year you retire may create minimum tax. Donation credits carry forward five years, so there is usually room to move.

Run T691 before you sign, not at filing time. The AMT calculation is mechanical and any competent tax software will produce it from a projection. The cost of finding out in April is that every structural option has closed.

Do not restructure a good transaction to avoid AMT that you will recover. If the seven-year test is comfortably met, minimum tax is a cash flow event. Paying advisory fees to avoid a timing difference is a poor trade.

What the AMT does not do

It does not apply to a corporation. Corporate minimum tax is a separate provincial concept and unrelated. It does not apply to most trusts in the way it applies to individuals, and graduated rate estates are treated distinctly, which matters when a share sale happens through an estate rather than in life. And it does not override the exemption itself: the lifetime capital gains exemption, which CRA indexes annually and puts at $1,275,000 for 2026 and $1,250,000 for 2025, still eliminates the regular tax. AMT reaches only 30% of the sheltered gain, at 20.5%, above an exemption that is itself substantial.

Put concretely, the reformed AMT is a narrower instrument aimed harder. Most people will never see it. The people who do will see it once, in a year that was already the most consequential financial year of their lives.

What to do

If you have a share sale, a property disposition, an option exercise or a significant in-kind donation anywhere in the next eighteen months, get a T691 projection built on your actual numbers before the transaction is committed. The variables that matter are the size of the preferential income, your ordinary income in that year, and your realistic income for the seven years after. All three are knowable in advance.

That projection is a tax exercise rather than an investment one, and it belongs with whoever will be preparing the return for the year the sale lands in.

If a sale or a donation is on your horizon and you would like the minimum tax modelled before the documents are signed rather than after, that is worth an early conversation.