The Tax Torpedo, IRMAA and Withdrawal Order: The Three Tax Mechanics Behind Retirement Income
Most retirement tax mistakes are not bracket mistakes. They come from three interactions that a tax return does not show you until the year after: how extra income taxes your Social Security, how income at 63 sets your Medicare premium at 65, and why the order you draw accounts in changes both.
What are the tax torpedo, IRMAA and withdrawal order, and why do they have to be planned together?
The tax torpedo is the band of income in which each additional dollar from an IRA withdrawal or Roth conversion also makes more of your Social Security benefit taxable, so the effective rate on that dollar exceeds your nominal bracket. IRMAA is Medicare's premium surcharge, set by the tax return from two years earlier, with thresholds that work as cliffs. Withdrawal order is the sequence in which you draw taxable, tax-deferred and tax-free accounts, which decides how much income lands in which year. They have to be planned together because each one changes the inputs to the other two: a conversion that looks fine in its own bracket can trigger the torpedo in that year and a Medicare surcharge two years later.
The Social Security tax torpedo.
Federal law taxes up to 85 percent of benefits, phased in by a formula that reaches back into other income.
Whether your Social Security benefit is taxed depends on provisional income: adjusted gross income, plus tax-exempt interest, plus half of the benefit. Above a first threshold, up to half the benefit becomes taxable; above a second, up to 85 percent does. The thresholds are set in statute and have not been indexed for inflation since they were written, which is why a growing share of retirees crosses them every year.
The torpedo is what happens inside those bands. Take an additional dollar from a traditional IRA. It is taxed as income. It also raises provisional income, which pulls more of the benefit into taxable income, and that slice is taxed too. Across the band where the phase-in is running, the effective marginal rate on the IRA dollar can be well above the bracket you think you are in. Once you are past the 85 percent ceiling the effect stops; below the first threshold it never starts. It bites in the middle, which is where most retired households sit.
The planning consequence: the torpedo applies only once benefits have started. Income taken before claiming, in the gap years, is not subject to it. That is one of the strongest reasons to decide claiming age and conversion timing together rather than one at a time. Confirm the current thresholds and your own position with your CPA; this is not tax advice.
IRMAA: the two-year look-back.
Medicare prices its premiums off a tax return you filed two years ago.
Medicare Part B and Part D premiums carry an income-related surcharge for households above thresholds that Medicare adjusts each year. The determination uses modified adjusted gross income from the return two years earlier, so the income you report at 63 sets your premium at 65, and a large Roth conversion or a lump-sum withdrawal in a single year can raise premiums for a full year two years out. The thresholds are cliffs: one dollar over a bracket triggers the whole year's surcharge for that bracket, for both spouses on a joint return.
Two practical rules follow. First, the IRMAA clock starts earlier than Medicare does, so conversions planned for the early 60s have to be modeled against the thresholds from age 63 onward, not from 65. Second, a life-changing event, such as retirement itself, can support an appeal to use a more recent year's income; the forms and rules are Medicare's, and the timing matters. Retiring in three years covers where the Medicare bridge and the IRMAA window sit in the 58-to-61 sequence.
Withdrawal order: why there is no universal answer.
Taxable first, then tax-deferred, then Roth is a rule of thumb. It is right for some households and expensive for others.
| Account type | How withdrawals are taxed | Required distributions | What it is best kept for |
|---|---|---|---|
| Taxable (brokerage, savings) | Capital gains on appreciation; interest and dividends annually | None | Early years and gap-year income at low rates; flexible access |
| Tax-deferred (traditional IRA, 401(k)) | Ordinary income on every dollar | Begin at 73, or 75 for those born in 1960 or later | Drawn or converted in low-bracket years so later RMDs do not force income up |
| Tax-free (Roth IRA) | Qualified withdrawals untaxed | None for the owner | The most flexible dollars: late-life spending, surviving-spouse income, heirs |
The conventional order spends taxable money first to let tax-deferred money grow. For a household with a large traditional balance that is often wrong, because it leaves the whole balance to be forced out as required minimum distributions at 73 or 75, in a few compressed years, on top of Social Security, in the torpedo band and above the IRMAA cliffs. Drawing or converting tax-deferred money earlier, in the gap years, can flatten that spike. For a household with a small traditional balance and large taxable gains, the conventional order can be exactly right. The sequence is the output of modeling your own brackets year by year; it is not something a rule can supply.
How the three interact in one decision.
A conversion is the clearest example, because it touches all three at once.
Suppose a household retires at 62 and considers converting part of a traditional IRA to Roth. The conversion is taxed in the year it happens, so the first question is which bracket it fills. If Social Security has already started, the second question is how much of the benefit the conversion pulls into taxable income, which can make the real cost far higher than the bracket suggests. If either spouse is 63 or older, the third question is whether the conversion crosses an IRMAA threshold and raises Medicare premiums two years later. And the conversion changes the withdrawal order going forward, because it moves money from the account with required distributions to the one without. Done in the right year, at the right size, a conversion can lower lifetime tax and give the surviving spouse flexible income. Done without modeling the other two mechanics, it can cost more than it saves.
Hudson sits on the Massachusetts line across the river from Nashua, and its pre-retirees tend to arrive at this decision with a Massachusetts employer in their history and a New Hampshire address today, so the state layer is added to the federal one: New Hampshire taxes none of this income, Massachusetts taxes most withdrawals and private pensions, and the household's plans for where to live decide which rules apply. For Hudson residents weighing a financial advisor, retirement planning and retirement income planning that model the three federal mechanics and the state question in one pass are the work. KBR Retirement & Investment Solutions serves Hudson from Londonderry, about fifteen minutes west on Route 102, and by video.
Whether you have a withdrawal plan at all.
Two documents, five minutes.
- Pull last year's tax return and your most recent Social Security statement
- Can you say which account next year's withdrawals come from, and in what bracket they land?
- Do you know what your provisional income will be once benefits start?
- Do you know which year's return will set your first Medicare premium?
- Do you know your projected required minimum distribution in the first year it applies?
- If any answer is no, the withdrawal plan does not exist yet, whatever the portfolio looks like
All three mechanics, in your numbers, with your CPA.
An independent, fee-only registered investment adviser in Londonderry, New Hampshire.
KBR Retirement & Investment Solutions, LLC is a registered investment adviser, paid only by its clients, that sells no products. Bernie Ross, in financial services since 1997, is the only person who advises clients. The tax path is modeled year by year from your own return: provisional income once benefits start, the IRMAA thresholds from 63 onward, the required-distribution projection, and the withdrawal and conversion sequence that comes out of them, coordinated with your CPA and documented so the reasoning can be revisited when tax law or circumstances change. Retirement income planning describes the work; Social Security planning covers the claiming side of the torpedo; registration and the current Form ADV are linked from Disclosures.
Common questions.
What is the Social Security tax torpedo?
The effect by which additional income, such as an IRA withdrawal or a Roth conversion, causes a larger share of your Social Security benefit to become taxable at the same time. Because the extra dollar is taxed and it also pulls more benefit into taxable income, the effective rate on that dollar can be well above your nominal bracket across a specific band of income. It applies only once benefits have started, which is one reason the years before claiming are often the better window for conversions.
What is IRMAA and how is it calculated?
IRMAA is the income-related monthly adjustment amount, a surcharge on Medicare Part B and Part D premiums for households whose modified adjusted gross income exceeds thresholds that are adjusted each year. The determination uses the tax return from two years earlier, so income in the year you turn 63 sets premiums in the year you turn 65. The thresholds are cliffs rather than slopes: one dollar over a bracket raises the full year's surcharge. Current thresholds are published annually by Medicare; confirm them with your CPA.
What age do I need to start taking required minimum distributions?
Under SECURE 2.0, required minimum distributions from traditional IRAs and workplace plans begin at 73, or at 75 for anyone born in 1960 or later. Roth IRAs have no lifetime required distributions for the owner. The years between leaving work and the first RMD are usually the lowest-income years available and the main window for Roth conversions.
Should I draw from taxable, tax-deferred or tax-free accounts first?
There is no universal order. The right sequence depends on your brackets in each year, when Social Security starts, the size of your traditional balances relative to future RMDs, the Medicare thresholds two years out, and what you want the surviving spouse and heirs to inherit. Rules of thumb such as taxable first, then tax-deferred, then Roth can be right for one household and expensive for the next door. The sequence is an output of modeling, not an input.
Should I do a Roth conversion before I retire?
Possibly, in the gap years between your last paycheck and the start of Social Security and RMDs, when taxable income is lowest and a conversion can be filled into a lower bracket. The costs to weigh are the tax paid now, the IRMAA effect two years later once you are near or past 63, the tax-torpedo effect if benefits have already started, and whether the converted money will stay invested long enough to recover the tax. Model all three mechanics together with your CPA; this is not tax advice.
What this connects to.
Six retirement income planning mistakes pre-retirees make
Where the tax-deferred trap sits among the other five.
What is retirement income planning, and why start early?
Accumulation versus decumulation, and the window that matters.
A fiduciary advisor's role in Social Security claiming
Claiming age as the first input to all three mechanics.
About the author
Bernie Ross is the founder of KBR Retirement & Investment Solutions, LLC, an independent, fee-only registered investment adviser in Londonderry, New Hampshire. He has worked in financial services since 1997 and personally handles the planning and services every client relationship. Read more about Bernie.
This article is general information and is not personalized investment, tax or legal advice. It does not consider your individual circumstances. Consult your CPA or attorney on tax and legal matters. Advisory services are offered through KBR Retirement & Investment Solutions, LLC, a registered investment adviser. Registration does not imply a certain level of skill or training. See Disclosures.
Model the three mechanics before the first withdrawal.
Bring last year's tax return and your Social Security statement. The first conversation costs nothing and commits you to nothing.
