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Your $1 Million Capital Gain Just Triggered a $23,000 AMT Bill Nobody Warned You About
A dentist in Burlington closes her practice this month for $1.25 million. Her accountant told her the Lifetime Capital Gains Exemption would eliminate the federal tax. It did. Then Form T691 arrived in the mail calculating a $23,000 Alternative Minimum Tax bill nobody mentioned during the sale planning.
This is the 2024 AMT overhaul working exactly as designed, and it's catching business owners, professionals selling practices, and anyone with a large one-time capital event off-guard. Here's what changed and how to calculate whether you're exposed.
How the New AMT Actually Works
The AMT is a parallel tax system. You calculate your tax two ways, regular and AMT, and pay whichever is higher. The AMT was redesigned effective January 1, 2024, to target what the Department of Finance called the "top 0.5%," but the mechanics catch a much wider band of taxpayers.
For 2026, the AMT exemption is $181,440. Subtract that from your AMT income base, then multiply the remainder by 20.5%. That's your AMT liability. If it exceeds your regular federal tax, you pay the difference.
The killer detail: capital gains are included at 100% for AMT purposes, not the 50% used in regular tax calculations. For someone with a $1 million capital gain who claims the LCGE and zeros out their regular tax, the AMT base is the full million minus the exemption ($818,560) at 20.5%, yielding roughly $167,805 in AMT. The regular tax is zero. The difference is the hit.
Most provinces have their own AMT as well. Ontario's adds another 3-4%. Quebec's is higher.
The Three Situations Where AMT Bites Hardest
Claiming the LCGE. The lifetime capital gains exemption for selling a small business or farm is $1,016,836 in 2025 (indexed annually). It eliminates regular tax. The AMT calculation treats the entire gain as income. A business owner selling for exactly the exemption amount and using it fully will still owe roughly $170,000 in federal AMT.
Donating appreciated securities. Donate $500,000 of publicly listed shares to charity and you get a donation tax credit that wipes out regular tax. Under AMT, two things change: the credit is only worth 50% of its regular value, and 30% of the capital gain ($150,000) is added back to the AMT base. The combination can create a six-figure bill.
Flow-through shares and investment interest. Deductions from flow-through shares (used heavily in mining and oil/gas investment) and carrying charges (interest on investment loans) are disallowed or limited under AMT. A Calgary professional with $200,000 in flow-through deductions and $80,000 in investment interest may have a regular tax bill of $15,000 and an AMT bill of $65,000.
The Seven-Year Recovery Window
AMT paid isn't lost forever. It's carried forward for seven years and can be used to offset regular tax in any future year where your regular tax exceeds your AMT. For an active professional continuing to earn $300,000+ annually, recovery is likely. For someone who retires immediately after the sale or moves into a lower-income phase, the AMT becomes a permanent cost.
Run the numbers before assuming recovery. A 52-year-old physician selling her practice and cutting back to three days a week may never generate enough future "regular tax" to recover a $40,000 AMT payment before the seven-year clock expires.
The Practical Workaround
Spread the gain. The capital gains reserve lets you defer a portion of a sale over up to five years if you're receiving installment payments. A $1 million gain taken all in one year triggers AMT. The same gain spread as $200,000 per year for five years may stay entirely under the AMT threshold because each year's gain is smaller relative to the exemption.
Timing donations matters. Making a large donation in the same year as a large capital gain maximizes AMT exposure because both hit simultaneously. Spread the donation over two or three years instead.
For business sales, consider an earnout structure where 60% is paid at close and 40% over three years. The deferred portion gets taxed in later years when your income profile is lower and AMT is less likely.
The AMT is now a liquidity-event tax for high earners. Plan the timing, or the bill shows up after you've already spent the proceeds.
A dentist in Burlington closes her practice this month for $1.25 million. Her accountant told her the Lifetime Capital Gains Exemption would eliminate the federal tax. It did. Then Form T691 arrived in the mail calculating a $23,000 Alternative Minimum Tax bill nobody mentioned during the sale planning.
This is the 2024 AMT overhaul working exactly as designed, and it's catching business owners, professionals selling practices, and anyone with a large one-time capital event off-guard. Here's what changed and how to calculate whether you're exposed.
How the New AMT Actually Works
The AMT is a parallel tax system. You calculate your tax two ways, regular and AMT, and pay whichever is higher. The AMT was redesigned effective January 1, 2024, to target what the Department of Finance called the "top 0.5%," but the mechanics catch a much wider band of taxpayers.
For 2026, the AMT exemption is $181,440. Subtract that from your AMT income base, then multiply the remainder by 20.5%. That's your AMT liability. If it exceeds your regular federal tax, you pay the difference.
The killer detail: capital gains are included at 100% for AMT purposes, not the 50% used in regular tax calculations. For someone with a $1 million capital gain who claims the LCGE and zeros out their regular tax, the AMT base is the full million minus the exemption ($818,560) at 20.5%, yielding roughly $167,805 in AMT. The regular tax is zero. The difference is the hit.
Most provinces have their own AMT as well. Ontario's adds another 3-4%. Quebec's is higher.
The Three Situations Where AMT Bites Hardest
Claiming the LCGE. The lifetime capital gains exemption for selling a small business or farm is $1,016,836 in 2025 (indexed annually). It eliminates regular tax. The AMT calculation treats the entire gain as income. A business owner selling for exactly the exemption amount and using it fully will still owe roughly $170,000 in federal AMT.
Donating appreciated securities. Donate $500,000 of publicly listed shares to charity and you get a donation tax credit that wipes out regular tax. Under AMT, two things change: the credit is only worth 50% of its regular value, and 30% of the capital gain ($150,000) is added back to the AMT base. The combination can create a six-figure bill.
Flow-through shares and investment interest. Deductions from flow-through shares (used heavily in mining and oil/gas investment) and carrying charges (interest on investment loans) are disallowed or limited under AMT. A Calgary professional with $200,000 in flow-through deductions and $80,000 in investment interest may have a regular tax bill of $15,000 and an AMT bill of $65,000.
The Seven-Year Recovery Window
AMT paid isn't lost forever. It's carried forward for seven years and can be used to offset regular tax in any future year where your regular tax exceeds your AMT. For an active professional continuing to earn $300,000+ annually, recovery is likely. For someone who retires immediately after the sale or moves into a lower-income phase, the AMT becomes a permanent cost.
Run the numbers before assuming recovery. A 52-year-old physician selling her practice and cutting back to three days a week may never generate enough future "regular tax" to recover a $40,000 AMT payment before the seven-year clock expires.
The Practical Workaround
Spread the gain. The capital gains reserve lets you defer a portion of a sale over up to five years if you're receiving installment payments. A $1 million gain taken all in one year triggers AMT. The same gain spread as $200,000 per year for five years may stay entirely under the AMT threshold because each year's gain is smaller relative to the exemption.
Timing donations matters. Making a large donation in the same year as a large capital gain maximizes AMT exposure because both hit simultaneously. Spread the donation over two or three years instead.
For business sales, consider an earnout structure where 60% is paid at close and 40% over three years. The deferred portion gets taxed in later years when your income profile is lower and AMT is less likely.
The AMT is now a liquidity-event tax for high earners. Plan the timing, or the bill shows up after you've already spent the proceeds.
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