Dear, Rusty: I am confused by an article in my local newspaper that said MAGI (modified adjusted gross income), on which my Medicare Part B premium is based, is my adjusted gross income, plus any nontaxable interest, plus 50% of the Social Security I received. The confusing part is the 50% part.

When I look at my tax return, my adjusted gross income includes the taxable portion of my Social Security benefit which, in my case, is 85% of my total benefits. Why must 50% of benefits be added to my AGI if it is already included in my total AGI?

Signed, Confused

Dear, Confused: The article you refer to was misleading for stating the modified adjusted gross income used to determine your Medicare premiums includes your normal adjusted gross income from your income tax return, plus any nontaxable interest you may have had, plus 50% of the Social Security benefits you received during the tax year. What the article should have said was the MAGI, which determines your income-related monthly adjustment amount to your Medicare premiums, consists of your normal AGI from your tax return, which includes the taxable portion of your Social Security benefits, plus any nontaxable interest you may have had.

For additional clarity, the IRMAA is a supplemental amount added to the standard Medicare premium for those with higher incomes. The thresholds at which the IRMAA supplements apply depend on your IRS filing status, and your MAGI determines the amount of supplement that will be added to the standard Medicare premium.

Single filers with MAGI over $103,000 or married filers with MAGI over $206,000 will see an IRMAA supplement added to their Medicare premium. Those whose MAGI is under the first IRMAA threshold pay the standard Medicare premium, but those whose MAGI exceeds the first IRMAA threshold above will pay more. How much more depends on how much their MAGI exceeds the first IRMAA threshold by.

The IRMAA supplement (the additional premium amount) could be anywhere from $69.90 to $419.30 per month for Medicare Part B (coverage for outpatient services) or an additional $12.90 to $81 per month to the Medicare Part D (prescription drug plan) premium — again dependent on how much over the initial MAGI threshold the person is for their IRS filing status.

IRMAA and MAGI can be confusing. If you have questions about your Medicare premiums, help is available at ssadvisor@amacfoundation.org or at 1-888-750-2622.

This article is intended for information purposes only and does not represent legal or financial guidance. It presents the opinions and interpretations of the AMAC Foundation’s staff, trained and accredited by the National Social Security Association. NSSA® and the AMAC Foundation and its staff are not affiliated with or endorsed by the Social Security Administration or any other governmental entity.

To submit a question, visit amacfoundation.org/programs/social-security-advisory or email ssadvisor@amacfoundation.org.

Editor’s Note: Russell Gloor received training from the National Social Security Association and was accredited by the NSSA® as a Social Security adviser in 2016. In addition to answering Social Security questions daily, he also authors the AMAC Foundation’s nationally syndicated weekly “Ask Rusty” advice column and has written three instructional books about Social Security.