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"Federal Insurance Contributions Act," Maria says. "[It's a] federal law that requires employees and employers to withhold back a portion of our paycheck and put it into a fund that—when we turn 65—will pay our Medicare and our Social Security benefits. So every two weeks you have to pay, as an employee, 7.65 percent of your check. Your employer will match that another 7.65 percent for a total of 15.2 percent. ... If you're self-employed, you're on the hook for the whole 15.2 percent."