Also called: LTCG, 0% capital gains bracket, qualified dividends
Gains on assets held more than one year, and qualified dividends, are taxed at 0%, 15% or 20% depending on taxable income. They stack on top of ordinary income when the rate is determined.
Because gains sit on top of ordinary income, adding ordinary income (for example a Roth conversion) can push gains that would have been taxed at 0% into the 15% rate.
Realizing gains deliberately while inside the 0% range raises cost basis at no federal tax cost. RetIQ calls this 0% Capital Gains Harvesting.