 Now, this is standard amount that all American workers pay and which, after enough credits are earned, allows you to collect Social Security benefits when you retire and permits you to enroll in Medicare Part A for free when you're 65. If you're self-employed, you pay a self-employment tax on your net earnings instead of a FICA tax, and you must pay both the employee and the employer portion of the tax, which comes out to be 15.3% total.