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How it’s calculated2026 figures

Medicare premiums and IRMAA

Part B and D premiums, IRMAA tiers and the two-year income lookback.

Updated

Where this happens in a plan year

2of 8 stages

  1. Events
  2. Growth
  3. Required
  4. Income
  5. Spending (covered)
  6. Cash flow
  7. Taxes (covered)
  8. Year end
On this page
  1. What you enter
  2. How premiums are calculated
  3. The two-year lookback
  4. The first Medicare year
  5. What isn’t modeled
  6. Reading the result

From the month each person turns 65, CoastMath adds Medicare premiums to household spending: the Part B standard premium, any income-related surcharge (IRMAA) on Parts B and D, and the Part D, Medigap or Advantage premiums you enter. The surcharge tier comes from the household’s modified AGI two years earlier, compared with the thresholds for the filing status on that earlier return.

For the plan’s first two years, that earlier income predates the projection, so CoastMath uses the prior-year figures you enter.

What you enter

  • Part B and Part D drug coverage switch those premiums and their surcharges on or off. Part B uses the published standard premium; you don’t enter it.
  • Part D plan premium and Medigap or Advantage premium are monthly amounts per person, in today’s dollars.
  • Apply income-related surcharges (IRMAA) turns the surcharge on. Below it, Last year’s modified AGI and Modified AGI two years ago set the first two years’ tiers, with the filing status of each of those returns.

Part A is assumed premium-free. If someone will pay a Part A premium, or their Medicare starts after 65, set that person’s Medical cost method to Coverage premiums + optional budget. Enter their Medicare-covered quarters for Part A, counting a spouse’s record if it qualifies them: with 40 or more there is no premium, with 30 to 39 the reduced premium applies, and with fewer the full premium applies. Other Part A premium ($ per month) is added on top, so leave it at 0 when you enter quarters. Those per-person settings, with Medicare starts at age, replace the shared Medicare choices for that person.

2026 Medicare premiums, per person per month
Part B standard premium
$202.90
Part A, fewer than 30 quarters of work
$565
Part A, 30–39 quarters
$311

How premiums are calculated

Annual Medicare premium, per person=(Part B + Part B surcharge + Part D surcharge + Part D plan + Medigap or Advantage)×Months enrolled

The surcharge tier is set once for the household from the lookback MAGI, and each enrolled person pays it. MAGI here is adjusted gross income, including IRA withdrawals, Roth conversions and realized capital gains.

2026 IRMAA tiers, per person per month
MAGI, individual returnMAGI, joint returnPart B totalPart D surcharge
$109,000 or less$218,000 or less$202.90$0.00
Over $109,000 – $137,000Over $218,000 – $274,000$284.10$14.50
Over $137,000 – $171,000Over $274,000 – $342,000$405.80$37.50
Over $171,000 – $205,000Over $342,000 – $410,000$527.50$60.40
Over $205,000 – $500,000Over $410,000 – $750,000$649.20$83.30
Above $500,000Above $750,000$689.90$91.00

Married filing separately and lived with your spouse at any time that year: $109,000 or less pays the standard premium; up to $391,000 pays $649.20 for Part B and $83.30 for Part D; above that, $689.90 and $91.00. Separate filers who lived apart all year use the individual column. The Part D surcharge is added to your plan’s premium.

In later years, the Part B premium, the surcharge amounts and the published Part A premium grow from their 2026 values at your medical cost inflation (plan inflation when blank). The income thresholds index with plan inflation, except that the top thresholds of $500,000 and $750,000 stay fixed through 2027, as the law requires. Part D, Medigap and Advantage premiums you enter grow at medical cost inflation.

Example: a couple two years after a $300,000 income year
Part B standard, 2 people × 12 months$202.90 a month each$4,869.60
+Part B surcharge, tier 2$202.90 a month each$4,869.60
+Part D surcharge, tier 2$37.50 a month each$900.00
+Part D plan premiums$40 a month each$960.00
+Medigap premiums$150 a month each$3,600.00
=Medicare premiums for 2028$15,199.20

Both 68 in 2028, filing jointly, 2026 MAGI of $300,000, no inflation. In 2029 the lookback is 2027, with no income, and the total falls to $9,429.60.

The two-year lookback

Each year’s tier uses MAGI from the tax year two years earlier. From the plan’s third year on, that is the projected MAGI CoastMath computed for that year. For the first two years it is what you entered:

  • First plan year uses Modified AGI two years ago.
  • Second plan year uses Last year’s modified AGI.

A blank field falls back to the current year’s income, with a warning. The thresholds are those for the filing status on the lookback return. For the first two years that is the status you enter; afterwards it is the projected status for that year. A surviving partner’s first premiums after a death therefore still use the joint thresholds of the last joint return.

Which tax year sets each year’s surcharge, plan starting 2026
Plan startsEntered: two years agoEntered: last yearProjected 2026 incomeProjected 2027 income2024202520262027202820292030

Year

Income in any projected year first affects premiums two years later.

Show data
Which tax year sets each year’s surcharge, plan starting 2026
Premium yearIncome year usedSource
20262024Modified AGI two years ago
20272025Last year’s modified AGI
20282026Projected
20292027Projected

Because of the lag, a Roth conversion or large sale at 63 already counts toward premiums at 65. See Roth conversions.

The first Medicare year

Medicare starts in the month of each person’s 65th birthday, or at the per-person start age you set, and that year’s premiums cover the remaining months. Someone born in July pays six months of Part B, $1,217.40 at the 2026 standard premium. For a couple, each person enrolls on their own birthday; a younger partner can stay on marketplace coverage, described in Marketplace coverage and premium tax credits, until their own 65th-birthday month.

What isn’t modeled

Reading the result

You seeCheckThen
A surcharge appears in a year when income is low.
The income two years earlier: a conversion, home sale or last working year.
The surcharge lasts one year per high-income year. See Roth conversions.
The first two years show a surcharge you don’t pay.
Whether the prior-year MAGI fields are blank; the warning says current income was used.
Enter both prior-year MAGI amounts and their filing statuses.
The tier changes the year after a partner dies.
The filing status of the lookback return. Individual-return thresholds are lower than joint ones.

Part B, Part D and Part A premiums, including surcharges, are qualified medical expenses for a health savings account; see Health savings accounts.

Next in Spending and healthcareOut-of-pocket medical costs and long-term care