The capital gains tax owed on a $300,000 profit depends entirely on the taxpayer's overall taxable income filing bracket, filing status (single, married filing jointly), and whether the asset was held for more than one year (long-term) or less (short-term). For long-term capital gains, federal rates are 0, 15, or 20 percent based on income thresholds, whereas short-term gains are taxed at ordinary income tax rates, which can reach up to 37 percent, alongside potential state-level income taxes.