IRMAA Surprise: How Your 401(k) Distribution Today Triggers Medicare Surcharges Two Years Later

A 66-year-old retiree with $1.4 million in a traditional 401(k) pulls $60,000 in 2026 to renovate a kitchen. Combined with $28,000 in Social Security and a modest pension, modified adjusted gross income lands at $112,000. Nothing dramatic happens on the 1040. In January 2028, the Medicare bill jumps.

That is the Income-Related Monthly Adjustment Amount, or IRMAA, at work. Medicare uses a two-year lookback on tax returns, so a distribution taken today sets premiums for 2028. Crossing the first threshold by a single dollar triggers the surcharge for all twelve months. Roughly 8% of Part B beneficiaries pay it, and the group skews heavily toward 401(k) holders drawing down accounts.

What the Threshold Actually Costs in 2026

The first IRMAA tier begins at modified adjusted gross income above $109,000 for individuals or $218,000 for joint filers. Crossing it raises the Part B premium from the standard $202.90 to $284.10 per month, an $81.20 monthly surcharge. Part D piles on another $14.50 per month. Roughly $1,148 a year for a single filer, before considering that both spouses in a couple pay the surcharge separately.

Push MAGI above $137,000 individual or $274,000 joint, and Part B climbs to $405.80 monthly. A married household straddling that middle tier faces a combined Part B and Part D surcharge running close to $1,783 a year, and that is before the tax bill on the withdrawal itself.

The Tax Cascade Nobody Prices In

The same distribution that lifts MAGI over $109,000 also drags Social Security into taxation. For a single filer with combined income above $34,000, up to 85% of benefits become taxable. Stack that on the 22% federal bracket, and the effective marginal rate on the next dollar out of the 401(k) climbs toward 40% once IRMAA and Social Security taxation are counted together.

The 2026 Social Security COLA of 2.8% pushes benefits higher every year while IRMAA thresholds lag. Income receipts on assets reached $4.3 trillion in the second quarter of 2026, up from $4.2 trillion a year earlier. Retirees are drifting into IRMAA territory without a discrete decision to do so.

The 2026 Wrinkle for Anyone Still Working

Workers 50 and older who earned more than $150,000 in 2025 must now route catch-up contributions into a Roth 401(k). The standard cap brings that group to $35,750. The forced Roth treatment removes the pre-tax deduction late-career savers built their plan around. It also builds a bucket of tax-free withdrawals that will never count toward future MAGI. That is the only lever most 401(k) holders have to shrink IRMAA exposure a decade out.

Three Moves Before December 31

1. Model MAGI to the dollar. If projected income lands within $5,000 of $109,000 (single) or $218,000 (joint), defer any remaining discretionary 401(k) distribution to January, or accelerate deductible expenses such as charitable gifts to compress the current-year figure. The rise in CPI from about 325 in January to nearly 334 in June 2026 tightens the real value of these thresholds every year.
2. Use a QCD once age 70½ hits. Qualified charitable distributions from an IRA count toward the required minimum distribution but never enter MAGI. The 2026 limit is $111,000 per person, and rolling 401(k) balances to an IRA first is the standard workaround, since 401(k) plans cannot originate QCDs directly.
3. File Form SSA-44 after a life-changing event. Retirement itself, the death of a spouse, or a work stoppage all qualify. Medicare will recalculate the surcharge based on current-year income rather than the two-year-old return, often erasing the premium jump entirely.

The distribution decision made in August 2026 is the Medicare bill opened in January 2028. The retirees who plan for the lookback keep the surcharge at zero. The rest write a check every month for a withdrawal they barely remember making.

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