Most people spend decades doing everything right. They max out their 401(k), resist the urge to dip into savings early, and tell themselves that retirement will be the payoff for all that discipline. What almost nobody talks about is the tax bill waiting at the other end.
The rules governing retirement income are a completely different game from the ones you played while you were working. Wages get replaced by a patchwork of income sources: Social Security, IRA withdrawals, a pension, maybe some investment income from a brokerage account. Each one has its own tax rules, and they interact with each other in ways that are rarely obvious.
The shift catches people off guard not because they weren’t paying attention, but because the system genuinely is confusing. A perfectly reasonable financial decision in one area – pulling a bit more from a traditional IRA to cover a home repair – can quietly trigger a cascade of tax consequences you didn’t see coming. The effects compound, and by the time they show up on your tax return, there’s often nothing you can do about them.
A Q1 2026 study from the Allianz Center for the Future of Retirement found that 70% of Americans are concerned about taxes on their income in retirement, a figure that climbed from 66% the previous quarter. The worry is warranted. What follows is a plain-English breakdown of the most common retirement tax traps, where they hide, and what you can actually do about them.
1. Assuming Your Social Security Is Tax-Free
Ask most people whether their Social Security benefits are taxable and they’ll say no – or at least, they’ll say they assumed they wouldn’t be. That assumption is one of the most expensive misconceptions in retirement planning.
If your combined income exceeds certain limits, a portion of your Social Security benefits may be taxable. According to SmartAsset’s 2026 guide on Social Security taxation, the threshold is $25,000 for single filers and $32,000 for married couples filing jointly. If your combined income – calculated as your modified adjusted gross income plus half of your Social Security benefits – exceeds these amounts, up to 50% or 85% of your benefits may be taxable.
These thresholds have not been inflation-adjusted since 1994. That’s not a typo. While almost everything else in the tax code gets nudged upward each year to account for rising prices, the Social Security taxation thresholds have sat at the same number for over thirty years. As benefits have grown and investment income has grown alongside them, millions more retirees have crossed into taxable territory without changing their behavior at all. A retiree can underestimate their total tax burden if they look only at the direct tax on a new withdrawal and ignore the extra Social Security taxation it can trigger.
One common mistake is thinking 85% is the tax rate rather than the taxable share of benefits. Another is forgetting to include tax-exempt interest in the combined income calculation. Municipal bond interest looks harmless because it’s federal-income-tax-free, but it still counts toward the combined income formula that determines how much of your Social Security gets taxed. The practical countermeasure is to track combined income before making any large withdrawals, and to consider whether Roth IRA distributions could meet some of those income needs instead. Roth distributions don’t count toward combined income, so they don’t increase the percentage of benefits that may be taxable.
2. Letting RMDs Catch You Off Guard
Required minimum distributions, or RMDs, are the IRS’s way of finally collecting on decades of tax-deferred growth. The government was patient while your traditional 401(k) and IRA balances compounded, but patience has a deadline.
You must take your first required minimum distribution for the year in which you reach age 73. The RMD rules apply to all employer-sponsored retirement plans, including profit-sharing plans, 401(k) plans, 403(b) plans, and 457(b) plans, as well as traditional IRAs and IRA-based plans such as SEPs, SARSEPs, and SIMPLE IRAs. RMDs are taxed at ordinary income rates – not the preferential long-term capital gains rates that apply to brokerage accounts. For someone who spent their career funneling pre-tax dollars into a 401(k), that can add up to a significant annual tax bill that appears right when income is supposedly at its simplest.
If you don’t take any distributions, or if the distributions are not large enough, you may have to pay a 25% excise tax on the amount not distributed as required, dropping to 10% if the RMD is corrected within two years, according to IRS RMD rules. RMDs as a percentage of your balance grow over time – roughly 3.7% at age 73, 5% at age 80, and 8% at age 90. That means the mandatory withdrawals accelerate, and so does the tax bill. Stacking RMDs on top of Social Security and any pension income can easily push a retiree into a higher federal bracket than they occupied during their working years. The window between retirement and RMD age – often a stretch of five to ten years in your early 60s – is the best time to start reducing the traditional account balance through strategic withdrawals or partial Roth conversions.
3. Relying on Only One Type of Account
Spending thirty years putting everything into a traditional 401(k) is understandable. Pre-tax contributions felt like an obvious win – lower taxable income every year, more money compounding. The problem reveals itself later: you end up with all your retirement savings in one tax bucket, and every dollar you pull out gets taxed as ordinary income.
Without a plan, it’s easy to default to withdrawing from the most accessible account, often a traditional IRA, without considering the tax impact. Tax-deferred accounts like traditional IRAs and 401(k)s have withdrawals generally taxed as ordinary income, while qualified withdrawals from Roth accounts are typically tax-free, and taxable brokerage accounts may generate capital gains, dividends, or interest depending on activity. The difference between those three categories is enormous when you’re managing a $30,000 unexpected expense or trying to fund a trip without crossing a critical tax threshold.
Diversifying across account types is really about giving yourself options. A retiree who can choose between a traditional IRA withdrawal and a Roth withdrawal in any given year has the ability to manage their taxable income deliberately. They can top up to the edge of a bracket with pre-tax dollars, then pull anything extra from the Roth, tax-free. Someone whose entire savings sits in one type of account doesn’t have that flexibility. The years before retirement – particularly the period before RMDs begin at 73 – are the most valuable for building that mix through partial Roth conversions, even if it means accepting some tax today.
4. Triggering the Medicare IRMAA Surcharge
IRMAA is an acronym most retirees have never heard until the letter arrives in the mail. It stands for Income-Related Monthly Adjustment Amount, and it’s Medicare’s version of a means test: if your income was high enough two years ago, you pay more for your Medicare Part B and Part D premiums today.
The Medicare surcharge in 2026 applies to beneficiaries with income exceeding $109,000 for single filers and $218,000 for joint filers. For these beneficiaries, total monthly Part B premiums range from $284.10 to $689.90, according to Kiplinger’s 2026 Medicare premium guide. Part D surcharges range from $14.50 to $91.00 per month. For a married couple where both spouses are on Medicare, the surcharge is applied individually, which means a single high-income year can add well over $10,000 in combined Medicare costs.
The two features of IRMAA that catch people most by surprise are the lookback period and the cliff structure. The surcharge is based on your modified adjusted gross income from two years ago – so your 2026 IRMAA liability is based on your 2024 income. By the time the notice arrives, there’s nothing you can do about the income that triggered it. IRMAA is a cliff surcharge, meaning you pay higher premiums if your MAGI exceeds a threshold by even one dollar. Realized capital gains, Roth conversions, and distributions from traditional IRAs are all events that can push you over a threshold without warning. A large Roth conversion is worth doing – but only if you know in advance what it will cost in Medicare premiums two years later.
5. Misunderstanding How Roth Conversions Work
Roth conversions are genuinely useful. Moving money from a pre-tax retirement account into a Roth IRA means paying tax on that amount now, but all future growth and withdrawals come out completely tax-free. Done well, this strategy can reduce future RMDs, lower IRMAA exposure, and give heirs a cleaner inheritance. Done carelessly, it can create a tax bill that wipes out the advantage.
Most people approaching retirement focus on the 12% and 24% bracket ceilings because the jumps above them – to 22% and 32% – are the steepest cliffs in the bracket structure. The goal of a smart Roth conversion is to fill a bracket without crossing into the next one. The 2026 inflation-adjusted brackets allow for conversions at slightly higher levels, with the 12% ceiling at $100,800 for married filers and the 24% ceiling at $403,550. That extra headroom matters when you’re trying to move pre-tax retirement dollars into a Roth account without pushing into a higher rate.
The IRMAA interaction is the most overlooked cost. A Roth conversion adds to your MAGI in the year it happens. If that conversion tips you over an IRMAA threshold, you’ll face higher Medicare premiums for the two years that follow. The optimal strategy often involves front-loading Roth conversions in years before Medicare enrollment – typically ages 63 to 64 – to keep income just below the first IRMAA threshold, then reducing conversion amounts once Medicare begins. Timing the conversion before Medicare enrollment, rather than after, is often where most of the benefit lives. A large conversion in your first year on Medicare, with no prior planning, can produce a surcharge bill that significantly offsets what you saved.
Read More: 35 Money Milestones You Should Hit for Retirement at Every Age
What to Do With All of This
None of these traps require heroic financial sophistication to avoid. What they require is awareness and timing – knowing the rules exist before the deadline, not after. Most of the damage happens because people are running a plan designed for their working years and haven’t updated it for the completely different mechanics of retirement income. The tax system for retirees isn’t cruel, exactly, but it does assume you know how it works. It won’t remind you.
The most consistent piece of advice threading through all five of these traps is the same: tax diversification. Having money spread across pre-tax accounts, Roth accounts, and taxable brokerage accounts gives you real choices when you’re drawing down income. It lets you pick the source of a withdrawal based on what makes sense for that tax year, that bracket, that IRMAA window, that Social Security combined income calculation. Nobody has perfect foresight, and tax law changes. But a retiree with account diversity can adapt. One who put everything in one bucket has to take whatever the rules hand them.
Retirement tax planning isn’t a one-time task. It’s closer to a recurring check-in – at least annual, and ideally before any decision that significantly changes your income for the year. A surprise RMD, an unexpected inheritance, the sale of a property: any of these can ripple across your Social Security tax, your Medicare premiums, and your bracket in ways that feel invisible until they land on your tax return. The good news is that for most of these traps, the window to act is not as narrow as people assume. The gap between when you retire and when RMDs start is often a decade. That’s a long time to make smart moves, if you know what you’re moving toward.
AI Disclaimer: This article was created with the assistance of AI tools and reviewed by a human editor.