Most retirees know Medicare Part B has a monthly premium. Fewer realize that a single tax return from two years ago can push that premium up by hundreds of dollars a month for an entire year. The mechanism is the Income-Related Monthly Adjustment Amount, or IRMAA, and its 2026 brackets have just come into focus for anyone approaching Medicare age or already enrolled.
How IRMAA Works in 2026
The Medicare Part B standard premium for 2026 is $202.90 per month. Beneficiaries whose modified adjusted gross income (MAGI) crossed a threshold on their 2024 tax return pay that base amount plus a surcharge on both Part B and Part D. The five-tier surcharge structure begins at $109,000 of MAGI for single filers and $218,000 for joint filers, and the top tier applies above $500,000 (single) or $750,000 (married filing jointly).
Part B surcharges range from $81.20 per month at Tier 1 to $487.00 at Tier 5. Part D surcharges add another $14.50 to $91.00 per month on top of a standalone drug plan premium that averages $34.50 nationally. Because IRMAA is applied per beneficiary, a married couple both enrolled in Medicare pays the surcharge twice.
The Two-Year Lookback
The Social Security Administration sets 2026 IRMAA using the most recent tax return the IRS has on file, which for most beneficiaries is the 2024 return. Premiums for 2027 will be set by 2025 MAGI. This lag creates a planning gap: a financial decision made today shows up in Medicare premiums two years later, often after the beneficiary has stopped thinking about the transaction that caused it.
The One-Dollar Cliff
IRMAA is not phased in. A single dollar of MAGI above a threshold moves the entire year into the next tier. Crossing the first cliff adds $81.20 per month to Part B and $14.50 per month to Part D, or roughly $1,148 per person per year. For a married couple, that is about $2,296 in surcharges triggered by one dollar of extra income. Moving from Tier 1 to Tier 2 costs a couple roughly $3,475 more per year.
Where Retirees Get Caught
Ordinary retirement moves trigger IRMAA more often than large one-time windfalls. The usual suspects include Roth conversions, required minimum distributions after age 73, capital gains from rebalancing or selling a rental, and the sale of a business. Because these events increase MAGI in the year they occur, the surcharge shows up two years later. Bogleheads forum threads regularly feature retirees who executed the "textbook" Roth conversion at age 63 or 64 and were surprised by a five-figure Medicare bill at 65 or 66.
Planning Around the Brackets
Front-load conversions before age 63. Because IRMAA has a two-year lookback and Medicare starts at 65, any Roth conversion completed in the tax year you turn 63 or earlier is invisible to your first Medicare premium. The window between retirement in the late 50s and age 63 is the most valuable Roth conversion runway a household will ever have.
Fill brackets deliberately. Rather than one large conversion, split the amount across multiple years to stay just under a bracket. A conversion that lands $500 above a threshold costs more in IRMAA than the last $500 of tax savings is worth.
Use QCDs after age 70½. Qualified charitable distributions from an IRA count toward RMDs but are excluded from MAGI, which can keep a charitably inclined retiree out of a higher bracket.
Appeal life-changing events. SSA Form SSA-44 lets beneficiaries request an IRMAA reduction after retirement, divorce, death of a spouse, or other qualifying events that reduce income below the lookback year.
The Bottom Line
IRMAA is a stealth tax on retirement income, and its two-year lookback punishes retirees who plan taxes one year at a time. The 2026 brackets, standard $202.90 Part B premium, and per-person surcharge structure make the math worth running before—not after—executing a Roth conversion, a large withdrawal, or a taxable-account sale. Coordinating account withdrawals, using tax-diversified buckets (including Roth accounts, taxable brokerage, and tangible assets), and tracking MAGI against the next bracket are the levers that keep Medicare costs from eating into retirement cash flow.
Sources: Kiplinger, Centers for Medicare & Medicaid Services, Social Security Administration, United Medicare Advisors, IRMAA Group