Capital Gains, Losses, and Adjusted Cost Base

Capital gains and losses are central to Canadian investment taxation because they determine how much of an investor’s portfolio growth is actually taxable when an asset is sold or otherwise disposed of. The calculation seems simple, but the exam is full of traps involving adjusted cost base, selling expenses, carryovers, superficial losses, and deemed dispositions.

Students should focus on three questions. What is the adjusted cost base? What event created the disposition? And if there is a loss, is it actually usable now or denied under the superficial-loss rules?

    flowchart LR
	    A[Buy identical property] --> B[Track ACB]
	    B --> C[Disposition or deemed disposition]
	    C --> D[Proceeds minus ACB minus selling costs]
	    D --> E[Capital gain or capital loss]
	    E --> F[Taxable capital gain or allowable capital loss]
	    F --> G[Apply carryback, carryforward, or denial rules]

Start with the Basic Formula

A capital gain or loss arises on a disposition of capital property. For many investors, the main examples are the sale of shares, mutual funds, ETFs, bonds held as capital property, and certain real estate investments.

The core formula is:

capital gain or loss = proceeds of disposition - adjusted cost base - selling expenses

This is simple in outline but detail matters.

Adjusted Cost Base

Adjusted cost base, or ACB, is the running tax cost of the property. It usually begins with purchase price plus acquisition costs such as commissions. It can then change over time.

Common ACB adjustments include:

• brokerage commissions on purchase
• reinvested distributions that increase tax cost
• return of capital that reduces tax cost
• averaging across identical properties bought at different times

The averaging rule is especially important. For identical properties, Canada does not let investors pick one particular lot casually for tax purposes. The ACB must usually be averaged across all identical holdings.

The Taxable Portion of a Capital Gain

Only the taxable portion of a capital gain is included in income. CRA’s currently published guidance for 2025 individual returns continues to use a 50% inclusion rate. The federal government has also announced changes for certain later periods, so real-world filers should always check the CRA instructions for the actual tax year being filed rather than relying on an older summary.

The practical exam point remains the same:

• a capital gain is not generally taxed in full like interest income
• a capital loss does not automatically offset every kind of income

Capital Losses and Carryovers

Capital losses produce allowable capital losses, not ordinary deductions against salary or interest. They are generally usable only against taxable capital gains.

If the investor has excess net capital losses, they can usually:

• carry them back up to 3 years
• carry them forward indefinitely

This makes losses valuable, but only in the right context.

Superficial Losses

The superficial-loss rule is one of the most tested topics in this area. A loss is generally denied if:

• the investor or an affiliated person buys the same or an identical property within the defined 30-day window before or after the sale, and
• the investor or affiliated person still owns the property at the end of that period

Affiliated persons can include:

• a spouse or common-law partner
• a corporation controlled by the taxpayer
• certain registered plans in related situations

The key practical point is that a loss is not always available just because the security was sold below cost.

Deemed Dispositions and Other Special Cases

Not every capital-gain event involves an ordinary sale.

Common deemed-disposition situations include:

• death
• gifts below fair market value
• certain changes in use
• certain trust or estate events

For exam purposes, students should remember that tax can be triggered even when there was no cash sale in the ordinary sense.

A related point is that a principal residence may qualify for its own exemption rules, but Chapter 24’s investment focus is mainly on capital property such as securities and investment real estate rather than on detailed housing elections.

Practical Investor Errors

Investors commonly make mistakes by:

• forgetting to include commissions in ACB
• ignoring reinvested distributions
• misreading cash flow from return of capital as tax-free profit forever
• assuming a loss is immediately deductible after buying back the same position

These are exactly the distinctions that separate a strong exam answer from a weak one.

Key Terms

• Disposition: sale or other event that triggers recognition of gain or loss
• ACB: adjusted cost base used to measure the tax cost of capital property
• Taxable capital gain: portion of the capital gain included in income
• Allowable capital loss: portion of a capital loss that can offset taxable capital gains
• Superficial loss: denied loss where the property is repurchased within the prohibited window and still held at the end of that period

Common Pitfalls

• calculating gain or loss without adjusting for commissions
• forgetting that identical properties use an averaged ACB
• assuming all capital losses can offset employment or interest income
• triggering a superficial loss by repurchasing too quickly
• overlooking deemed dispositions

Key Takeaways

• Capital gains and losses depend on proceeds, ACB, and selling expenses.
• ACB must be tracked carefully over time, especially for identical securities and return-of-capital adjustments.
• Capital losses generally offset taxable capital gains, not ordinary income.
• Superficial-loss rules can deny a loss even when the investment was sold below cost.
• Inclusion-rate rules can change by tax year, so current CRA instructions always matter for real filing.

Quiz

Sample Exam Question

An investor sells shares at a loss in her non-registered account on December 15. Her spouse buys the same shares on December 20 and still owns them in late January.

Which statement is strongest?

• A. The loss is fully deductible against salary because the sale occurred before year-end
• B. The loss is superficial and is generally denied because an affiliated person repurchased the identical property within the prohibited period and still held it at the end
• C. The loss is automatically converted into an RRSP deduction
• D. The loss is ignored only if the original investor repurchases the shares personally

Correct answer: B.

Explanation: The spouse is an affiliated person. Repurchase inside the defined window while the identical property is still owned at the end of the period usually triggers the superficial-loss rule.