Is there a deadline?

Yes, and it may be sooner than you think. For a loss to count in the current year, the trade has to settle on or before Dec. 31. Because the settlement date is three business days after the trade date, and because Christmas Day and Boxing Day are statutory holidays, the last day for tax-loss selling of Canadian stocks this year is Dec. 24. If you sell after that date, the loss will be recorded for tax purposes in the following year.