Old-Age, Survivors, and Disability Insurance is a federal program otherwise known as Social Security. OASDI, or FICA (Federal Insurance Contribution Act) taxes are withheld from your paycheck to fund Social Security and Medicare. For 2021, the Social Security base tax rate is 6.2%, and the Medicare tax rate is 1.45%. Both the employee and employer pay the same amount, which is based on employee’s earnings.