Changes to the tax code change how gains on qualified small business stock (QSBS) are excluded from income, shorten the minimum holding period to 3 years, and let certain converted convertible bonds count as QSBS with the bond holding time tacked onto the stock holding period. The law also revises S corporation and related aggregation/passive-loss rules to reflect the new QSBS treatment. Most changes apply prospectively to stock acquired or convertible debt issued after enactment.