For example, a single filer crossing $109,000 in modified AGI or a married couple crossing $218,000 triggers the first IRMAA tier. This might sound high until you add it up: $45,000 annually in Social Security, $40,000 in dividend income, and $35,000 in IRA withdrawals put a single retiree at $120,000.Medicare premiums are not fixed, and higher-income retirees can pay more through Income-Related Monthly Adjustment Amounts, known as IRMAA. These surcharges apply to both Part B (medical insurance) and Part D ...