Roth Conversions and IRMAA: How to Convert Without Crossing a Cliff

How a conversion reaches your Medicare bill

A Roth conversion is taxable income in the year you do it, so it appears in your adjusted gross income and in your modified adjusted gross income for IRMAA. Social Security will see it on your return two years later. A conversion made in 2026 is counted for 2028 premiums; one made in 2027 is counted for 2029. Conversions before age 63 never touch your Medicare premiums, which is why the years between retirement and 63 are a favorite conversion window.

Converting also has a long-term IRMAA benefit. Money in a Roth IRA is not subject to required minimum distributions during your lifetime, and qualified Roth withdrawals do not count toward MAGI. Shrinking a large traditional IRA lowers future RMDs, which are one of the most common reasons retirees land in IRMAA tiers in their late 70s.

Your headroom at different income levels

Headroom is the largest amount you can add without changing tier. The table uses the 2026 brackets; your real limit for a 2026 conversion will be the 2028 brackets, which should be somewhat higher because the limits rise with inflation. Using today's limits leaves you a built-in cushion.

Roth conversion headroom on the 2026 brackets, by MAGI before converting
MAGI before converting	Individual return	Joint return
$80,000	$29,000	$138,000
$100,000	$9,000	$118,000
$120,000	$17,000	$98,000
$150,000	$21,000	$68,000
$175,000	$30,000	$43,000
$200,000	$5,000	$18,000

Notice that headroom does not shrink steadily as income rises. A single filer at $120,000 is already in tier one but has $17,000 of room before tier two, more than the $9,000 a filer at $100,000 has before tier one. What matters is where you sit inside your tier, which is why the Roth headroom finder asks for your exact income.

A worked example

Linda is single, 67, and has $100,000 of MAGI from a pension, Social Security and dividends. She wants to move $120,000 from her traditional IRA to a Roth over the next few years.

$9,000Her headroom before the first cliff
$37,000Her headroom if she accepts tier one
$1,148Yearly cost of choosing tier one

Converting $9,000 a year keeps her on the standard premium but would take more than a decade. Converting $37,000 a year takes her MAGI to exactly $137,000, the top of tier one, so she pays $1,148.40 more in Medicare premiums for each of those years, but she finishes in about three years. Converting $38,000 would push her one dollar into tier two and cost another $1,736.40 on top. The sensible choices are $9,000 or $37,000; anything in between pays the tier-one cost without using the room it buys.

When crossing a cliff is worth it

IRMAA is a cost, not a veto. A conversion that crosses a cliff can still make sense when:

Your future tax rate will be higher. If RMDs, a pension and Social Security will push you into a higher tax bracket later, or if you expect tax rates to rise, paying some IRMAA now can be cheaper than the future tax.
You are filling a whole tier. As in Linda's example, once you accept a tier, convert enough to use all of its room.
Your heirs face high tax rates. Non-spouse heirs generally must empty an inherited traditional IRA within ten years, often during their peak earning years. A Roth passes to them tax-free.
A spouse is likely to be widowed. The survivor will face the individual limits, half the joint ones. Converting while you still file jointly uses the wider joint tiers.

The comparison is simple to state: the extra IRMAA for the year versus the tax you expect to save on the converted dollars over time. A financial planner or tax professional can run the full projection; the headroom number tells you exactly where the cost changes.

A yearly routine

In the fall, estimate the year's MAGI without the conversion, including December fund distributions.
Find your headroom, and leave a cushion of a few thousand dollars.
Convert in December, when the year's other income is known.
Remember the conversion cannot be undone: recharacterizations of conversions are no longer allowed.
Repeat next year with the new brackets.

Enter your income and see the largest conversion that keeps your tier.

Open the Roth headroom finder

Frequently asked questions

Does a Roth conversion count as a life-changing event for IRMAA?

No. A conversion is income you chose to create, so Form SSA-44 cannot remove it. Plan the size before you convert.

Can I undo a conversion that pushed me over a cliff?

No. Since 2018, Roth conversions cannot be recharacterized back to a traditional IRA.

Do Roth withdrawals count toward IRMAA later?

Qualified Roth IRA withdrawals are not included in adjusted gross income, so they do not raise MAGI.

When is the best time to convert?

Before 63 a conversion does not affect Medicare premiums at all. After that, late in the year, when the rest of your income is known, lets you size it to your headroom.

Roth conversions and IRMAA: how to convert without crossing a cliff