How does a Roth conversion in 2025 change IRMAA surcharges for Medicare Part B and D?

1. Why a 2025 Roth conversion matters for Medicare in 2027

Medicare sets IRMAA using MAGI from tax returns filed two years earlier. Multiple sources state that taxable events in 2025 will be reflected in the IRMAA determination for the 2027 premium year — so a Roth conversion in 2025 increases your 2025 MAGI and therefore can trigger higher Part B and Part D surcharges in 2027 ^{[2] [5]}. Advisers and calculators warn that what looks like a single-year tax planning move has a delayed Medicare cost consequence ^{[2] [5]}.

2. How much can premiums jump — the scale of the surcharge exposure

The IRMAA surcharge structure is tiered and “cliff”-like: exceeding a threshold by one dollar can move you to the next bracket and sharply increase your annual Medicare costs ^[5]. Kiplinger quantifies the range of extra expense in 2025: from roughly $888 to $5,326.80 per year for Part B and $164.40 to $1,029.60 per year for Part D depending on which tier you hit ^{[3] [4]}. Analysts show concrete examples: a large conversion can add thousands annually and persist for the affected year because the SSA uses the two‑year lookback ^{[6] [1]}.

3. What counts toward IRMAA MAGI — why Roth conversions are visible

For IRMAA purposes, MAGI equals your AGI plus tax‑exempt interest; taxable Roth conversions are included in AGI the year they occur, so they directly raise IRMAA MAGI ^{[7] [8]}. Financial-planning pieces repeatedly note that conversions from traditional IRAs or 401(k)s to Roth IRAs are taxable transactions and therefore risk bumping you into higher Medicare premium brackets ^{[8] [9]}.

4. Timing, planning and the “three‑year” caution

Several outlets emphasize timing: because IRMAA looks back two years, conversions should be planned well before you need lower MAGI. Kiplinger and advisers suggest converting years before Medicare enrollment or smoothing conversions across years to avoid cliff effects ^{[3] [4]}. One practical rule found in sources: a conversion done three years before applying for Medicare can reduce the chance that Roth distributions or the conversion itself will count against the two‑year lookback used to set premiums ^[3].

5. Strategies reported by planners — tradeoffs and limits

Sources propose multi-year, smaller conversions rather than one large conversion, using Qualified Charitable Distributions (QCDs) or other offsets to keep MAGI under thresholds, and running “what-if” IRMAA calculators before acting ^{[2] [6]}. Planners warn these moves have tradeoffs: spreading conversions reduces immediate tax efficiency, and other tax-law interactions (SALT caps, QBI, etc.) can change the optimal plan, especially for high-net-worth taxpayers ^{[10] [5]}.

6. Appeals and exceptions the sources mention

If a one-time event caused a jump in income, the SSA allows beneficiaries to request a redetermination if you can demonstrate a life-changing event or an unusual spike in income; commentators note appeals can sometimes reduce or remove an IRMAA surcharge for that year ^[11]. Sources also say IRMAA applies to both Original Medicare and Medicare Advantage enrollees and is deducted automatically from Social Security benefits for most people ^{[11] [12]}.

7. Bottom line and practical next steps

If you consider a Roth conversion in 2025, model the effect on your 2025 MAGI and then on the 2027 IRMAA tiers using calculators or an adviser; small adjustments (convert a little less, shift timing, use QCDs) can keep you below costly thresholds ^{[2] [6]}. The literature consistently shows conversions are powerful tax tools but can trigger significant, delayed Medicare premium increases if not carefully timed ^{[1] [4]}.

Limitations: available sources do not provide IRS or Social Security numeric tables for every 2027 IRMAA tier yet; analysts infer impacts using current brackets and calculators (noted planners and tools cited above) ^{[2] [13]}.