You pay the Part B premium each month. Most people will pay the standard premium amount. However, if your modified adjusted gross income as reported on your IRS tax return from 2 years ago is above a certain amount, you may pay more.
Your modified adjusted gross income is your taxable income plus your tax exempt interest income. Social Security will notify you if you have to pay more than the standard premium. If you have to pay a higher amount for your Part B premium and you disagree (even if you get RRB benefits), call Social Security at 1-800-772-1213. TTY users should call 1-800-325-0778.