FICA — the Federal Insurance Contributions Act — is the payroll tax line on every paycheck that funds Social Security and Medicare. It's not one tax but two combined into a single deduction, and it's split between you and your employer. * The total rate is 15.3% of wages, and it's divided equally: your employer pays half, you pay half. Your share as an employee breaks down to 6.2% for Social Security and 1.45% for Medicare, for a combined 7.65% taken out of every paycheck. Your employer matches that same 7.65% separately, on top of your gross pay — it's not deducted from what you see on your pay stub. * The two pieces behave differently at high incomes. Social Security tax only applies up to an annual wage cap that adjusts each year — earn above that cap, and you stop paying Social Security tax on the excess for the rest of the year. Medicare tax has no cap at all; it applies to every dollar you earn, no matter how high your income climbs. * High earners actually pay more than the standard rate on the Medicare side. An Additional Medicare Tax of 0.9% kicks in on wages above $200,000 in a calendar year — and unlike the standard Medicare tax, employers don't match this additional portion; it's entirely on the employee. * Self-employed workers pay both halves themselves through a separate but related tax called SECA, since there's no employer to split the cost with — which is part of why self-employment tax often comes as a surprise to people transitioning from a traditional paycheck.