Does the Lifetime Capital Gains Exemption Trigger AMT in Ontario?

You have a buyer for your corporation, you believe your shares qualify for the lifetime capital gains exemption (LCGE), and you expect little or no tax. Then someone mentions alternative minimum tax. It is fair to ask whether a claim that looks tax-free on paper can still produce a bill.

This article explains in plain language how AMT treats a gain sheltered by the exemption, how to tell whether it is worth running the numbers, and what planning options generally exist. It is general information for Ontario sellers, not a calculation of your tax.

First, the exemption amount you are working with

The LCGE limit is $1,250,000 for dispositions of qualifying property after June 24, 2024. It was increased to that amount for qualified small business corporation shares and qualified farm or fishing property, and indexation resumes in 2026. For dispositions in 2026 the CRA lists the limit as $1,275,000, which is the $1.25 million base indexed by 2.0%.

The CRA also describes the maximum capital gains deduction as $625,000, which is 50% of the $1,250,000 limit. The deduction and the limit are different numbers, so check which one a calculation or article is using. Because the figure depends on the year of sale, confirm it for your closing date.

How AMT treats a gain you have sheltered

AMT is a parallel calculation that runs next to your regular tax. Your minimum amount is worked out as A(B − C) − D, where A is 20.5%, B is your adjusted taxable income, C is the AMT exemption threshold and D is the basic minimum tax credit. If that minimum amount is higher than your regular federal tax, the difference is the extra tax you pay.

Two rules matter for a business sale. For AMT, the capital gains inclusion fraction is read as 1/1, so capital gains are included at 100% in adjusted taxable income. And the deductions under s. 110.6(2) and (2.1), which are the capital gains deductions, are counted at 7/5.

Put together, 100% inclusion less a deduction counted at 7/5 of the usual taxable portion leaves a net AMT inclusion of 30% of gains sheltered by the LCGE. That 30% is an arithmetic result of those two provisions rather than a number written in the statute, so treat it as a rule of thumb and have your accountant confirm it against your own figures.

When is it worth checking for AMT?

Not every seller owes AMT. For 2025, the CRA says an individual whose test amount is $177,882 or less probably does not owe minimum tax, and that above that amount Form T691 may be needed. Taxable capital gains on line 12700 and the capital gains deduction on line 25400 are among the amounts that trigger the check. That figure is for 2025, so look up the threshold for your year of sale.

Form T691 is the form used to calculate federal tax payable under AMT. The capital gains deduction itself is calculated on Form T657 and claimed on line 25400 of the T1 return. A large gain, even a mostly exempt one, is a good reason to have an accountant run a T691 estimate before you sign, not after.

The AMT credit in s. 127.531 is also limited. For example, only one-half of certain non-refundable credits under s. 118 and four-fifths of the donation amount under s. 118.1 count toward it. This means credits you normally rely on may not offset AMT as fully as they offset regular tax.

Recovering AMT and planning around it

AMT paid is not necessarily lost. Under s. 120.2(1), unused additional tax from the 7 preceding taxation years can be deducted from tax payable in a later year, but only to the extent regular tax exceeds that year's minimum amount. If the sale is a one-time event and your income is modest in later years, the recovery may be slow or only partial, so do not assume you will get it all back quickly.

Common planning questions to raise with your advisers include:

• Would a capital gains reserve spread the gain over several years instead of one? The general reserve limits the amount you can defer so that gain is brought into income over at least 5 years.
• Do you qualify for a longer reserve? The reserve extends to 10 years for qualified small business corporation shares sold to a child resident in Canada, and in other listed cases such as certain intergenerational transfers, employee ownership trust sales and cooperative conversions.
• Would a different closing date change which year the gain falls in, and what your other income is that year?
• How does a reserve interact with claiming the deduction in the year the gain is included? This needs to be modelled, because the answer depends on your facts.

Also keep in mind that AMT is only part of the picture. Ontario personal tax applies to the taxable portion after the federal deduction, and how Ontario handles AMT-related interactions depends on your situation, so ask your accountant to model the combined result.

What to do next

• Confirm the year your sale closes and the LCGE limit for that year.
• Ask your accountant to estimate regular tax and AMT side by side, including Form T657 and Form T691.
• List your non-refundable credits and donations, since only part may count against AMT.
• Find out whether a reserve is available for your type of sale and buyer.
• Review the details with a tax professional or lawyer before signing the purchase agreement, while the structure can still change.

Frequently asked questions