When during the year is the best time to harvest tax losses?

You can harvest anytime, but many investors sweep for losses during market dips throughout the year rather than waiting for December, since a temporary drop may recover before year-end. Continuous or opportunistic harvesting captures losses that a once-a-year December check would miss. That said, a year-end review is still smart to lock in losses before the December 31 deadline and to net them against realized gains you've booked during the year. Watch the wash-sale window: don't rebuy the same security within 30 days on either side, which can bump a late-December harvest into January complications. Coordinate harvesting with any planned gain realizations so the losses land where they save the most tax.