The Retirement Tax Trap: How RMDs, Social Security, and Medicare Work Together

By: Alex Bridges, CFP®, EA, ChFC®, RICP®

Many retirees I work with at Tiverton Wealth in The Woodlands and across Greater Houston spent 30 years doing what they were told: max out the 401(k), take the pre-tax deduction, and let it grow. That advice often made sense during the working years. Retirement can feel different.

Required minimum distributions, the taxation of Social Security, and Medicare premiums were each written as separate rules. In practice they all look at the same number: your income. Pulling one lever can move all three at once. That is what I call the retirement tax trap.

This article is for retirees and near-retirees, roughly ages 60 to 72, who hold most of their savings in pre-tax accounts. It is especially relevant if you have not yet reached your first RMD year, because that window is when many of the most useful planning decisions are still open.

What is the “retirement tax trap”?

The trap is the way one dollar of extra income in retirement can be counted several times. A traditional IRA withdrawal is taxed as ordinary income. It can also make more of your Social Security benefit taxable, and it can push your Medicare premiums into a higher bracket two years later.

None of these rules is hard to follow on its own. The difficulty is that they interact. A withdrawal that looks like it falls in the 12% or 22% bracket can carry a higher effective cost once the knock-on effects are counted.

How do required minimum distributions work?

Under Internal Revenue Code Section 401(a)(9), as amended by the SECURE 2.0 Act, most owners of traditional IRAs and employer plans must begin taking required minimum distributions (RMDs) at age 73. For people born in 1960 or later, the starting age is scheduled to rise to 75. The IRS explains the calculation and deadlines in IRS Publication 590-B.

RMDs are calculated by dividing your prior year-end balance by a life-expectancy factor from IRS tables. If the balance keeps growing through your 60s, the required withdrawals can be larger than you expect, and they are taxed as ordinary income whether you need the cash or not.

One detail catches people off guard. You may delay your first RMD until April 1 of the following year, but your second RMD is still due by December 31 of that same year. Two distributions in one tax year can stack income in exactly the way this article warns against.

Why can Social Security benefits become taxable?

Under IRC Section 86, up to 50% or up to 85% of your Social Security benefits can be included in taxable income. Which applies depends on your “provisional income.” The IRS walks through the calculation in IRS Publication 915.

Provisional income is your adjusted gross income, plus tax-exempt interest, plus half of your Social Security benefits. For married couples filing jointly, the base thresholds are $32,000 and $44,000. For single filers, they are $25,000 and $34,000.

Those thresholds are written into the statute and are not adjusted for inflation. As a result, a growing share of middle-income retirees find that much of their benefit is taxable.

What is the Social Security “tax torpedo”?

In the income range where benefits are being phased into taxation, each additional dollar of IRA income can pull 50 or 85 cents of Social Security into taxable income along with it. In the 85% phase-in range, a $1,000 IRA withdrawal can add up to $1,850 of taxable income.

That is why a retiree’s effective marginal rate in this range can be noticeably higher than the bracket printed on the tax table. Outside the phase-in range, the effect disappears. Knowing where you sit is the first step.

How does retirement income affect Medicare premiums?

Medicare Part B and Part D premiums include an Income-Related Monthly Adjustment Amount (IRMAA) for beneficiaries above certain income levels. The Social Security Administration determines IRMAA using modified adjusted gross income (MAGI): your AGI plus tax-exempt interest, as reported on your tax return from two years earlier. The SSA explains the rules in its publication Medicare Premiums: Rules for Higher-Income Beneficiaries.

IRMAA works in tiers, and each tier is a cliff rather than a gradual phase-in. Exceeding a threshold by a single dollar can trigger the full surcharge for that tier, for both spouses if each is on Medicare. Current-year thresholds and premiums are published annually at Medicare.gov.

Why does the two-year lookback matter for new retirees?

Because of the lookback, income you report at age 63 can affect the Medicare premiums you pay at 65. A final year of salary, a large bonus, a deferred compensation payout, or a sizable Roth conversion can all show up on that later premium bill.

If your income dropped because of a qualifying life-changing event, such as retirement or a reduction in work, you can ask the SSA to use more recent income with Form SSA-44. Many retirees do not know this form exists.

How do RMDs, Social Security, and Medicare interact?

Here is the chain reaction in plain terms. An RMD or IRA withdrawal raises your AGI. A higher AGI can make more of your Social Security taxable, which raises AGI again. The resulting MAGI is what Medicare uses, two years later, to set your premiums.

A single withdrawal decision can therefore touch your federal income tax, the share of your benefits that is taxable, and your Medicare costs. That is why I generally evaluate retirement withdrawals as a multi-year tax projection rather than one year at a time.

Where does the new senior deduction fit in?

The One Big Beautiful Bill Act added a temporary deduction for taxpayers age 65 and older, generally available for tax years 2025 through 2028. It is designed to reduce taxable income for many seniors, but it phases out as modified adjusted gross income rises. The IRS summarizes these provisions on its One Big Beautiful Bill provisions page.

For planning purposes, this is one more income-sensitive provision. Additional IRA income may raise your bracket, your taxable Social Security, and your IRMAA tier, and it can also shrink this deduction.

What are the “gap years,” and why do they matter?

The gap years are the period between retiring and the start of RMDs, and often before you claim Social Security. For many Houston-area retirees this runs from around age 60 or 62 into the early 70s. Taxable income can be unusually low during these years, sometimes lower than it will ever be again.

That low-income window can be useful for deliberately realizing taxable income at lower rates. Common approaches are planned IRA withdrawals or partial Roth conversions. The goal is not to minimize this year’s tax bill. It is to consider your lifetime tax picture, including the RMDs and Social Security income still ahead.

There are trade-offs. Income from age 63 onward feeds the IRMAA lookback. If you buy coverage through the ACA marketplace before 65, extra income can also reduce premium tax credits. Each of these should be modeled before acting.

What strategies may help manage the interaction?

No single approach fits every household. Depending on your circumstances, these are among the tools worth evaluating with a qualified professional:

• Partial Roth conversions in lower-income years. Converted amounts are taxable now. Future qualified Roth withdrawals generally do not count toward RMDs, provisional income, or MAGI. Whether conversions make sense depends on current and expected future tax rates, which no one can predict with certainty.

• Coordinating Social Security claiming with withdrawals. Drawing from IRAs earlier while delaying benefits can change the income mix in later years. It can also increase your eventual benefit.

• Qualified charitable distributions. Starting at age 70½, IRA owners may give directly to qualified charities under IRC Section 408(d)(8). The QCD can count toward your RMD and is excluded from income, as described in IRS Publication 590-B.

• Managing capital gains and asset location. Capital gains and investment income in taxable accounts also count toward AGI and MAGI, so their timing matters.

• Filing an IRMAA appeal when eligible. Form SSA-44 may help if a life-changing event lowered your income.

What is the “widow’s penalty,” and how does it relate?

After the death of a spouse, the survivor generally files as a single taxpayer starting the year after death. Single-filer brackets, Social Security thresholds, and IRMAA tiers are all lower than joint thresholds. Household income often falls less than those thresholds do.

For married couples with large pre-tax balances, this is one reason to think about reducing those balances while both spouses are living.

Is retirement tax planning different for Texas retirees?

Texas has no state income tax, so for most retirees in The Woodlands, Spring, Conroe, and the rest of Greater Houston, federal rules are where the planning happens. That keeps the analysis simpler in one way. It also means the RMD, Social Security, and IRMAA interactions are the main income-tax levers to work with.

Texas retirees often face significant property tax bills and insurance costs. Those expenses affect how much income needs to come out of retirement accounts each year, and that brings us back to the same three systems.

How can a fee-only fiduciary advisor help?

Because these rules interact, the analysis tends to work best when investment, withdrawal, and tax decisions are reviewed together. A fiduciary financial planner should project income several years ahead and test scenarios, such as converting more, less, or nothing at all, before any money moves.

Under the Investment Advisers Act of 1940, as interpreted in the SEC’s 2019 Commission Interpretation Regarding Standard of Conduct for Investment Advisers, registered investment advisers owe clients a fiduciary duty. CFP® professionals are also bound by the fiduciary duty in the CFP Board’s Code of Ethics and Standards of Conduct.

Tiverton Wealth, LLC is a fee-only Registered Investment Advisor based in The Woodlands, TX. It provides retirement planning and investment management for individuals and families across Greater Houston. As a fee-only firm, Tiverton Wealth does not earn commissions on products it recommends.

About the Author

Alex Bridges, CFP®, EA, ChFC®, RICP®, is the founder of Tiverton Wealth, LLC, where he focuses on retirement income and tax-aware planning for families in The Woodlands and Greater Houston. You can learn more about the firm’s approach at tivertonwealth.com.

You can review my full regulatory background on the SEC’s Investment Adviser Public Disclosure website: Alex Bridges — IAPD record.

This article is provided by Tiverton Wealth, LLC for general educational and informational purposes only. It does not constitute personalized investment, tax, or legal advice, and should not be relied upon as a substitute for advice from a qualified professional familiar with your specific circumstances. Tiverton Wealth, LLC is a fee-only Registered Investment Advisor providing services only in jurisdictions where it is properly registered or exempt from registration. Investing involves risk, including the possible loss of principal, and no strategy can guarantee a profit or protect against loss. Past performance is not indicative of future results. Please consult with a qualified financial, tax, or legal professional before making decisions based on this content.

Frequently Asked Questions

At what age do required minimum distributions begin?

Under the SECURE 2.0 Act, RMDs generally begin at age 73 for people born between 1951 and 1959, and at age 75 for people born in 1960 or later. IRS Publication 590-B has the details.

Do IRA withdrawals make Social Security taxable?

They can. Traditional IRA withdrawals increase provisional income, which determines whether up to 50% or up to 85% of Social Security benefits are taxable under IRC Section 86. See IRS Publication 915.

Which year’s income does Medicare use to set IRMAA?

Medicare generally uses modified adjusted gross income from your tax return two years before the premium year. If a qualifying life-changing event reduced your income, you may request a redetermination using Form SSA-44.

Do Roth conversions affect Medicare premiums?

Yes. Roth conversion income is included in MAGI for the year of conversion, so it can affect IRMAA two years later. Qualified Roth withdrawals in later years generally do not count toward MAGI.

Can qualified charitable distributions help reduce taxable income?

For IRA owners age 70½ or older, qualified charitable distributions made directly to an eligible charity can count toward RMDs and are excluded from taxable income, subject to annual limits and IRS rules.