Premium-free Medicare Part A is automatic if you are a U.S. citizen/legal resident age 65 or over and have been living in the U.S. for at least five years; if you and/or your spouse or ex-spouse earned 40 credits working for 10 years where Social Security was deducted from your payroll check and if you choose to receive your social security or railroad retirement benefits at 65 years or age or earlier.