The level of earnings to which the full Social Security tax applies. For 2013, the full 15.30 percent tax (the combined rate paid by employers and employees) applies to the first $113,700 of wages or self-employment income, and the 2.9 percent Medicare portion applies to all income over that level. (Employees pay part of the tax—5.65 percent up to the wage base limit and 1.45 percent after that—and their employers pay the other half. Self-employed taxpayers have to pay both halves.)