Cost basis what you paid for an investment; your gain or loss is measured from it. Where it's taught Tax-Loss Harvesting: Turning a Loser Into a Tax BreakCapital Gains: Why Holding On (and Trading Less) Beats the Tax Try it with a calculator Tax Loss Harvest CalculatorCapital Gains Calculator Related terms $3,000 ordinary-income offsetAsset locationCapital gainCapital loss / gainCarry-forwardLong-term gainRealized vs. unrealizedRealized vs. unrealized gain