The IRS taxes gains on stocks differently depending on how long you held the shares before selling. If you owned the stock for more than one year, any profits you realize will be taxed at the long-term capital gains rate, which is lower than the rate applied to ordinary income. If you held the shares for less than a year, your gains will be taxed at your marginal tax rate. In either case, you will also owe taxes on any dividends you receive from the stock. Keep good records of your stock purchases and sales so you can accurately calculate your tax liability come tax time.