Tax-loss harvesting, often called tax-loss selling, is a strategy available to investors holding non-registered investments such as stocks, bonds, mutual funds, and ETFs that have decreased in value below their purchase price. By selling these investments, investors can realize a capital loss, which can be applied to offset capital gains incurred during the same tax year. Additionally, these capital losses can be carried back to any of the three preceding tax years or carried forward indefinitely to offset future capital gains.