Eager to lock in your gains on a hot investment? Before you click on sell, consider the tax implications. In a taxable account, you'll pay 15 percent in capital gains taxes every time you sell a winner you've owned for more than a year (the longer you can defer paying taxes, the more time you're giving your money to grow). Come tax time, however, it can be a good move to sell losers in your portfolio to take advantage of the annual $3,000 capital-loss deduction limit and offset any capital gains on your winning picks.