Know the Rules
Some investments, such as fast-growing stocks, can generate substantial capital gains. These gains are recognized and generally taxable when you sell a security for more than you paid for it.
If you’ve owned that asset for over a year, you qualify for the long-term gains rate, generally 15 or 20 percent. The long-term gains rate also applies to qualified dividends. In contrast, short-term gains on investments held a year or less, are taxed at your ordinary-income tax rate–which is usually higher. Non-qualified dividends and interest income are also generally subject to your ordinary-income rate. The 3.8 percent net investment income tax (NIIT) might also apply depending on your income.
But if an investment is held in a tax-deferred account, like a traditional IRA, 401(k) or 403(b), it isn’t taxed until the money is taken out. It is then taxed at the tax rate you qualify for when you take it out, but the NIIT won’t apply to retirement plans.