How Investment Losses Reduce Your Lifetime Capital Gains Exemption

You expected to shelter a large gain on the sale of your corporation shares. Then your accountant tells you the available exemption is lower than the published limit. The reasons are often investment expenses from decades ago or business losses you claimed in earlier years.

This article explains in plain language how those reductions work, which forms are involved, and what you can do about it. It is general information for Ontario owners, and your own numbers need to be worked out with an accountant.

The headline limit and why you may not get all of it

The lifetime capital gains exemption (LCGE) limit is $1,250,000 for dispositions of qualifying property after June 24, 2024. For dispositions in 2026 the CRA lists $1,275,000, which is the $1.25 million base indexed by 2.0%. The maximum capital gains deduction is $625,000, which is 50% of the $1,250,000 limit.

Earlier deduction limits were different: $508,418 for 2024 dispositions before June 25, 2024, and $485,595 for 2023. If you claimed the exemption in earlier years, that usage counts against what is left, and the calculation is built on a cumulative gains limit.

The statute lets an individual deduct the least of three listed amounts for a year. That is why the number on your claim can be lower than the headline limit even when your gain is large: whichever of the amounts is smallest controls.

The two reductions: ABILs and CNIL

Two separate items commonly cut the exemption. The annual gains limit is reduced by your allowable business investment losses (ABILs) for the year. The cumulative gains limit subtracts your cumulative net investment loss (CNIL) at the end of the year.

If CNIL is zero, it does not reduce your deduction. A positive CNIL does. ABIL-related reductions can also carry into the cumulative calculation and last beyond the year of the loss, so a loss you claimed years ago may still matter. How that works for you is something your accountant should confirm from your tax history.

What counts as CNIL in everyday terms

CNIL is a running tally. Section 110.6(1) defines it as the amount, if any, by which your cumulative investment expenses exceed your cumulative investment income, measured from 1988 on. In plain words, if over the years you deducted more investment costs than the investment income you earned, that gap can reduce your exemption.

Because the tally goes back to 1988, many owners are surprised. Interest on money borrowed to invest, or investment expenses deducted in earlier years, can have built up a balance that you no longer remember. Which expenses and which income count are technical questions, so look at your actual returns rather than guessing.

CNIL is calculated on Form T936, which is required if you had investment income or expenses in any year from 1988 to 2025. The capital gains deduction itself is calculated on Form T657 and the allowable amount is claimed on line 25400 of your T1 return.

What you can do about a smaller exemption

There is no single fix, and what is available depends on your facts. Common questions to ask with your accountant, ideally before the sale closes:

• Has anyone calculated your CNIL on Form T936 for the year of sale, and does it match your records?
• Did you claim any ABILs in past years, and how do they affect your cumulative limit?
• Will other investment income or expenses in the year of sale change your CNIL at year end, which is when it is measured?
• If the exemption will not cover the whole gain, would a reserve spread the remaining gain over several years? The general reserve requires gain to be brought into income over at least 5 years, and certain sales can use a 10-year reserve.
• Is alternative minimum tax likely to apply to the sheltered portion? That can be a separate cost to plan for.

Timing can matter because CNIL is measured at the end of the year. Whether any change in your investment position is possible or sensible is a tax planning question for a professional, and steps taken only to change the number can be questioned, so do not act on a guess.

What to do next

• Gather your past returns, especially years with investment income, investment expenses, or business investment losses.
• Ask your accountant to prepare Form T936 and a draft Form T657 for your expected year of sale.
• Compare the result to the published limit and ask why any difference exists.
• Confirm the sale year and the limit that applies to it.
• Have a lawyer or tax professional review the sale structure before you sign, since the expected exemption affects how much tax you plan to owe.

Frequently asked questions