Tax on the profit from selling an investment for more than you paid.
In the US, gains on assets held more than a year are taxed at long-term rates of 0%, 15% or 20%; shorter holdings are taxed as ordinary income. In the UK, gains above a £3,000 annual allowance are taxed at 18% or 24%, while ISAs and pensions are sheltered. Many European countries apply flat rates – 26.375% in Germany, 27.5% in Austria.