First identify the account and tax residence
This guide is for a Canadian tax resident selling an investment in a non-registered account. A sale inside a TFSA generally does not create a taxable capital gain or deductible capital loss, while RRSP, RRIF, FHSA, corporate, trust, non-resident, and business-trading situations follow different rules.
The distinction between an investor and a securities trading business also matters. This workflow assumes capital treatment; frequent or business-like trading can be treated as business income instead.
Use proceeds minus ACB and selling costs
The basic capital gain is proceeds of disposition minus the adjusted cost base and outlays or expenses incurred to sell. Acquisition commissions normally increase ACB, while selling commissions reduce the gain as disposal expenses.
For foreign shares, calculate each transaction in Canadian dollars using an appropriate exchange rate for that date. A USD profit and a CAD taxable gain can differ, so converting the final USD gain at today's rate is not a reliable shortcut.
Average the cost of identical taxable holdings
Shares of the same class are generally identical properties. When identical shares are bought at different prices, CRA guidance requires an average ACB per share that is updated after purchases; selling shares reduces quantity but does not change the remaining per-share ACB.
Track taxable holdings across brokers rather than relying on one platform's displayed cost. Reinvested distributions, returns of capital, transfers, gifts, inheritances, and corporate actions can all change the ACB that belongs in Schedule 3.
Apply the inclusion rate, then the marginal tax rate
Canada does not apply one flat capital-gains tax rate to the sale. The current enacted inclusion rate is 50%, so one half of a net capital gain is generally included in taxable income; the government confirmed in Budget 2025 that it would not proceed with the proposed inclusion-rate increase.
The taxable capital gain is then subject to the investor's federal and provincial or territorial marginal income-tax rates. A useful estimate therefore needs province, other taxable income, and deductions instead of multiplying the full gain by a national headline percentage.
Use capital losses in the correct period
Allowable capital losses generally offset taxable capital gains, not ordinary employment income. A remaining net capital loss can generally be carried back to the three previous years or carried forward to future years, subject to the inclusion-rate adjustment rules for the years involved.
The estimate should include current-year gains and losses and any loss balance available on CRA records. An unrealized loss in another holding does not reduce tax until a disposition occurs and the loss is not denied.
Test every loss for the superficial-loss rule
A loss can be superficial when you or an affiliated person acquires the same or identical property from 30 calendar days before through 30 days after the sale and still owns it 30 days after the sale. Affiliated persons can include a spouse or common-law partner and certain controlled entities.
The denied loss is often added to the substituted property's ACB when the rules permit. Check automatic reinvestments and registered accounts as well as the account where the sale occurred before treating the loss as currently deductible.
Worked example: convert the gain into taxable income
Assume proceeds of C$20,000, an average ACB of C$12,000, and C$100 of selling expenses. The capital gain is C$7,900. With no other gains or losses, a 50% inclusion rate produces a taxable capital gain of C$3,950.
At an illustrative combined marginal rate of 30%, estimated tax is C$1,185. Cash after the C$100 selling expense and estimated tax is C$18,715. The real result depends on province, total income, credits, losses, and whether capital rather than business treatment applies.
What the Portle estimate should ask and show
Inputs should include residence and province, account type, investor or business treatment, shares sold, proceeds, selling costs, total quantity and ACB of identical taxable shares, transaction currencies and dates, annual gains and losses, loss carryovers, and possible replacement purchases. Results should show ACB per share, gain, included taxable gain, assumed marginal rate, estimated tax, and after-tax sale cash.
Official references: CRA Guide T4037 Capital Gains (canada.ca/en/revenue-agency/services/forms-publications/publications/t4037.html), CRA guidance on adjusted cost base and superficial losses, and the Department of Finance 2026 tax-expenditure report confirming the proposed inclusion-rate increase was not pursued. This is an educational estimate, not tax advice.