IRMAA

Most people pay the standard Part B premium, $202.90 a month in 2026, which covers about 25% of the program’s cost; the government pays the rest. With IRMAA, higher-income enrollees pay 35%, 50%, 65%, 80% or 85% of that cost instead. A matching surcharge is added to Part D drug coverage, tied to the national base premium rather than to your own plan’s price. CMS says roughly 8% of people with Part B pay it.

Social Security decides whether you owe it, using income data from the IRS, and sends you a letter with the amount. The income measure is modified adjusted gross income in its IRMAA form: adjusted gross income plus tax-exempt interest, with a few rarely used exclusions such as foreign earned income added back. On a joint return, the couple’s combined MAGI sets the tier, and each spouse on Medicare pays the surcharge.

The Part D surcharge is taken from your Social Security payment however you pay your drug plan, or billed separately if your benefit is too small or hasn’t started. IRMAA applies with Original Medicare, with or without a Medigap policy, and with Medicare Advantage, though Medigap’s own premiums carry no surcharge.

The table below shows the six 2026 tiers. The individual column applies to single, head of household and qualifying surviving spouse returns, and to married people filing separately who lived apart all year. Each tier is a cliff, not a phase-in: one dollar over a threshold charges that tier’s whole surcharge for the entire year, for each enrolled person. For a married couple both enrolled in Part B and Part D, moving from $218,000 to $218,001 of MAGI costs $2,296.80 for the year.

Married people who lived with their spouse at any point in the year but file separately face a harsher table, one of the costs of married filing separately. It has only three tiers: no surcharge at $109,000 or less, $446.30 for Part B and $83.30 for Part D above $109,000 and under $391,000, and $487.00 and $91.00 from $391,000 up. The $391,000 line is the $500,000 top threshold minus the $109,000 single threshold, as the statute prescribes.

The thresholds below the top tier rise each year with the consumer price index, rounded to the nearest $1,000, so compare future income with future thresholds, not 2026 ones. The top-tier lines of $500,000 and $750,000 are frozen by statute until 2028, when they start rising with inflation too.

IRMAA runs on a lag. Your 2026 premiums are based on the tax return you filed in 2025 for 2024. If the IRS had only your 2023 return when Social Security set your premium, you can give Social Security your 2024 figures to update it. The lag matters most around retirement: the last full year of salary can set a surcharge two years later, when your income has already fallen.

Social Security will use a more recent year if your income dropped because of a life-changing event. Qualifying events are marriage, divorce or a spouse’s death, stopping or cutting back work, losing income-producing property to a disaster or other event beyond your control, the end or reorganization of an employer pension, and a settlement from an employer’s closure, bankruptcy or reorganization. You report it on Form SSA-44 with documentation such as a letter from your employer. A voluntary one-time spike, such as a big Roth conversion or selling a rental, is not on the list.

If you later amend the return that set your premium, send Social Security the amended return and the IRS acknowledgment so it can correct your IRMAA.

IRMAA is rarely caused by wages alone once people have retired. It is usually triggered by one-time income or by income that grows quietly each year, and because the lookback is two years, the income that sets your first surcharge often arrives at 63, before you have even enrolled in Medicare. Since every tier is a cliff, it pays to know how far your MAGI sits below the next line before any large transaction. The most common triggers are:

The goal is not to avoid IRMAA at any cost but to price it alongside income tax. Because each tier is flat, a couple’s Roth conversion that crosses the first joint threshold by $1,000 triggers the same surcharge as one that crosses it by $50,000. Trimming a conversion to stay under a line usually pays; if you do cross one, filling the rest of that tier costs no more surcharge. A conversion that deliberately lands a tier higher for a year or two can still be worth it if it shrinks later required distributions that would trigger surcharges every year.

Some levers lower MAGI directly. From age 70½, a qualified charitable distribution sends IRA money to charity without it counting as income. Qualified Roth withdrawals and spending from cash or basis don’t add to MAGI. Spreading a large gain or conversion over several years can keep each year under a threshold, and planning the thresholds together with the Social Security tax torpedo and bracket edges shows where the next dollar is truly expensive.