Tax-loss harvesting means selling a losing position to realize a capital loss you can use against gains — then immediately replacing it to stay invested.
In Canada, the superficial-loss rule disallows the loss if you or an affiliated person repurchases the identical security within 30 days before or after.
The workaround: swap into a substantially different fund with similar exposure. Sell VCN.TO, buy XIC.TO. Sell VTI (US), buy VUN.TO (hedged) or a similar-but-not-identical proxy.
Only applies in non-registered accounts. TFSA/RRSP gains and losses are tax-irrelevant.
Track your book value carefully — brokerages report "book cost" but you are responsible for your own ACB on foreign securities and after superficial-loss adjustments.