Quick Read

  • A $52,000 CSRS pension plus $40,000 TSP withdrawal and restored Social Security quietly pushes a single retiree’s MAGI into the $109,000 IRMAA tier.

  • IRMAA operates as a hard cliff, costing roughly $1,150 extra per year in Medicare premiums the moment income crosses the threshold by even $1.

  • Rolling a TSP into an IRA unlocks qualified charitable distributions at age 70, letting retirees reduce MAGI without cutting their lifestyle or spending.

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The Civil Service Retirement System (CSRS) pension provides a reliable paycheck every month. So a retired United States Postal Service (USPS) manager feels pretty secure. Then a Medicare premium notice arrives showing a surcharge he had never seen before. A pension withdrawal can push a federal retiree across an Income-Related Monthly Adjustment Amount (IRMAA) line.

This scenario shows up on the federal retirement discussion boards every January, when new IRMAA letters land. The mechanics are almost always the same. For many federal retirees, the Social Security Fairness Act is bringing more money each year. But that often means modified adjusted gross income (MAGI) raises the Medicare bill.

A Case Study

  • Age and status: 68, retired USPS manager, single filer, enrolled in Medicare Parts B and D.

  • Guaranteed income: $52,000 CSRS pension, fully taxable as ordinary income with no preferential treatment.

  • Portfolio: $720,000 Thrift Savings Plan (TSP) balance, currently drawing $40,000 per year.

  • New variable: Restored own-record Social Security benefit after Windfall Elimination Provision (WEP) repeal, roughly $18,000 to $22,000 annually.

  • What is at stake: Medicare Part B and Part D surcharges that compound for life and shrink the net value of every TSP dollar withdrawn.

CSRS pays well because it was designed as a full retirement system, not a Social Security supplement. Every dollar lands on the 1040 as ordinary income. Add a $40,000 TSP draw, also fully taxable, and the running total is already $92,000. Layer on roughly 85% of a newly restored Social Security check, and MAGI lands in the $109,000 to $137,000 band for single filers. That is the second IRMAA tier on the 2026 CMS table, the first one that carries a surcharge.

Story Continues

The cost is real. The standard 2026 Part B premium is $202.90 per month. Crossing into that band adds an $81.20 monthly Part B surcharge, lifting the total to $284.10, plus a $14.50 Part D IRMAA. That is roughly $1,150 a year in extra Medicare cost triggered by being a few thousand dollars over the threshold. Think of IRMAA as a cliff; one dollar over the line and the full surcharge applies.

The income tax math compounds the squeeze. Under the 2026 brackets, a single filer pays 22% on income over $50,400 and 24% on income over $105,700, against a $16,100 standard deduction. Every marginal TSP dollar gets taxed at 22% or 24% and can drag MAGI into the surcharge zone.

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Two Moves that Could Change the Outcome

  1. Roll the TSP to an Individual Retirement Account (IRA) to unlock qualified charitable distributions. The TSP does not support QCDs, but an IRA does. Once he reaches age 70.5, he can route up to the annual QCD limit directly to charity, and that distribution counts toward the required minimum distribution (RMD) starting at 73 without hitting AGI or MAGI. For a CSRS retiree already giving to a church or veterans group, a $5,000 to $10,000 QCD can keep MAGI under the next IRMAA cliff without changing his lifestyle. The rollover should be a direct trustee-to-trustee transfer to preserve creditor protections and avoid withholding.

  2. Calibrate TSP withdrawals to the IRMAA threshold. Consider drawing less than $40,000. The disciplined version is to back into the maximum TSP withdrawal that keeps MAGI comfortably $3,000 to $5,000 below the next tier, using the prior year’s tax return and an estimate of taxable Social Security. If a big-ticket expense requires more cash, pull it in a year he plans to be over the cliff anyway, rather than spreading the overage across two surcharge years.

What to Do This Quarter

Pull last year’s 1040, add the restored Social Security amount, and recompute MAGI against the $109,000 single-filer threshold. If the number lands within $5,000 of the line, trim the December TSP withdrawal or shift it into January. The common mistake is assuming the Social Security Fairness Act was pure upside. Yes, the benefit went up but so did the IRMAA exposure, and the CSRS pension’s full taxability never changed. The retiree who models both sides of that trade keeps the raise. The one who does not hands a portion of it back to Medicare every month for the rest of his life.

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