Tax-loss harvesting in Canada — how it works and when to use it

Most Canadian investors know that capital gains are taxable. Fewer know that capital losses are a tool — one sitting in plain sight inside their non-registered accounts every time a position drops below what they paid for it. Tax-loss harvesting is the practice of deliberately selling those losing positions to realize a capital loss that offsets taxable capital gains, reducing what you owe the CRA in the same year. It is not a loophole. It is a strategy explicitly permitted under the Income Tax Act, used by Canadian investors at every level of portfolio size. Here is how it works, what the rules actually are, and where most investors trip over the superficial loss rule.

What tax-loss harvesting actually does

When you sell an investment in a non-registered account for less than your adjusted cost base (ACB) — your original purchase price, adjusted for any additional buys — you realize a capital loss. The CRA allows that loss to offset capital gains dollar for dollar.

A capital loss can be applied in three ways. First, it can offset capital gains realized in the same tax year, reducing your taxable gain directly. Second, it can be carried back up to three years to offset gains you already paid tax on — which triggers a refund from the CRA. Third, it can be carried forward indefinitely to offset future gains. The loss does not expire.

One important limitation: capital losses can only offset capital gains. They cannot reduce dividend income, interest income, or employment income. If you have no capital gains in the current year and no gains in the prior three years to carry back against, the loss sits in reserve until you have a gain to use it against.

A worked example

Sarah holds two positions in her non-registered account. Earlier in the year she sold a Canadian bank ETF for a $20,000 capital gain. She also holds shares in a sector fund she bought for $18,000 that are now worth $10,000 — an $8,000 unrealized loss.

Without tax-loss harvesting, Sarah owes tax on $20,000 in capital gains. At the 50% inclusion rate, $10,000 is added to her taxable income. At a 43.41% combined marginal rate (Ontario, income between $100,000 and $150,000), her tax bill on the gain is $4,341.

If Sarah sells the sector fund before year-end, she realizes the $8,000 capital loss. That loss offsets $8,000 of her $20,000 gain, leaving a net capital gain of $12,000. At the 50% inclusion rate, $6,000 is now added to taxable income instead of $10,000. Her tax bill drops to $2,605 — a saving of $1,736 from a single sell order.

The superficial loss rule — the one rule that matters most

The CRA does not allow investors to sell a position at a loss and immediately buy it back just to generate a tax deduction. This is enforced through the superficial loss rule. A loss is considered superficial — and therefore denied — if the identical security is purchased within 30 calendar days before or after the sale. The total restricted window is 61 days centred on the sale date.

The rule extends beyond just the investor. If your spouse or common-law partner buys the identical security within that 61-day window, the loss is denied. The same applies to corporations you control and, critically, to registered accounts. If you sell a stock at a loss in your non-registered account and your spouse purchases the same stock inside their TFSA within 30 days, your capital loss is superficial and cannot be claimed.

When a loss is denied as superficial, it is not permanently lost. The denied amount is added to the adjusted cost base of the repurchased security, deferring the loss until that position is eventually sold in a qualifying transaction.

How to maintain market exposure during the 30-day window

The practical problem with the superficial loss rule is that stepping out of a position for 30 days means missing any recovery in that security during that window. The solution is to replace the sold security with a similar but not identical one during the restricted period.

For example, if you sell a broad Canadian equity ETF at a loss, you could immediately purchase a Canadian dividend ETF from a different provider that tracks a different index. The two funds offer similar market exposure but are not identical securities — the superficial loss rule does not apply. After the 30-day window closes, you can switch back to your original holding if you choose.

The key test is whether the replacement security is genuinely different: different issuer, different underlying index, different economic exposure. Two ETFs tracking the exact same index from different providers may be considered identical by the CRA. When in doubt, choose a replacement with a meaningfully different mandate.

When tax-loss harvesting makes sense — and when it does not

Tax-loss harvesting is most useful when you have realized capital gains in the same tax year that the loss would directly offset. The math is immediate and certain. It is also useful when you expect to realize significant gains in a future year — banking a loss now creates a reserve you can deploy against those future gains.

It is less useful if you have no current or recent capital gains to offset and no clear near-term trigger for future gains. The loss will carry forward indefinitely, but a loss sitting unused for years has an opportunity cost — the capital that was tied up in the losing position is now redeployed, which is often the more important consideration.

It is not useful at all inside registered accounts. Selling at a loss inside a TFSA or RRSP generates no capital loss that can be applied against anything. The CRA does not recognize capital gains or losses inside registered accounts — which is exactly why those accounts shelter growth from tax in the first place.

The year-end deadline

Capital losses must be realized in the tax year to apply against that year's gains. With Canada's T+1 settlement standard, trades settle the business day after execution. For 2026, the final day to execute a tax-loss harvest that settles within the calendar year is December 30. Trades executed on December 31 will settle in January 2027 and fall into the next tax year.

Most investors review their non-registered accounts in November and December to assess positions sitting at a loss and determine whether any capital gains are in play for the year. A position at a $5,000 loss with $12,000 in realized gains elsewhere is a straightforward harvest. A position at a $5,000 loss with no gains to offset requires more thought about whether the carryforward is worth the friction of the trade.

Run the numbers before you act

The tax benefit of harvesting a loss depends on the size of the loss, your marginal rate, and what gains you have to offset. The run your capital gains number at Prospyr lets you enter your gain and province to see exactly how much tax is owed before any offsets. Run it with your full gain first, then subtract your harvested loss from the gain and run it again — the difference is your tax saving. That number tells you whether the harvest is worth executing before year-end.

The takeaway

Tax-loss harvesting is one of the few strategies that lets Canadian investors reduce tax without changing their long-term portfolio direction. The mechanics are straightforward: sell a losing position in a non-registered account, realize the capital loss, and apply it against capital gains from the same year or the prior three. The one rule that trips most investors is the superficial loss provision — do not repurchase the identical security within 30 calendar days before or after the sale, and coordinate with your spouse to avoid triggering the rule through their accounts.

The strategy only works in non-registered accounts. Inside a TFSA or RRSP, losses are not recognized by the CRA and cannot be used to offset anything. For investors building a dividend portfolio alongside a non-registered growth account, tax-loss harvesting is a natural annual step — review in November, act before December 30, and carry any surplus losses forward against future conversion gains.