What Is a Retirement Tax Bomb?

Quick Answer

Withdrawals from tax-deferred 401(k) plans and IRAs can create an avalanche of taxable income in retirement. Required minimum distributions, additional sources of income, Medicare surcharges and more can make retirement tax planning more complicated—and potentially more expensive.

Elderly couple planning retirement on laptop

Approximately 71% of non-retired adults are at least moderately worried about being able to fund their retirement, a 2023 Gallup poll found. But what if you're not worried about having enough money saved? What if you've set aside millions in tax-deferred 401(k) plans and traditional individual retirement accounts (IRAs)?

Don't stop worrying yet. Some successful retirement savers find themselves facing big tax bills after they retire. Distributions from tax-deferred IRAs and 401(k)s create taxable income. Investment gains and side income add to the mix, while high-income retirees may be hit with additional taxes on Social Security benefits and surcharges on Medicare premiums. When your tax bill is higher in retirement than it is during your working years, you may have a retirement tax bomb on your hands.

What Is a Retirement Tax Bomb?

Retiring from your job doesn't mean you get to retire from paying taxes. The taxes you've put off through pre-tax retirement contributions and tax-deferred earnings come due in retirement.

If you've saved pre-tax money in a tax-deferred 401(k) or traditional IRA, you'll pay regular income taxes on the full amount of your withdrawals when you retire.

The conventional wisdom is that your tax bracket will drop (or at least stay the same) in retirement, so squaring up with Uncle Sam won't be so bad. But some retirement super-savers have a different challenge: an avalanche of taxable income.

Although every situation is unique, here are some of the common components of a retirement tax bomb:

  • Taxable distributions that add up: Distributions, including required minimum distributions (RMDs) from your 401(k) and traditional IRA accounts, are fully taxable. If you have large or multiple accounts, your combined distributions may be sizable.
  • RMDs that rise over time: RMDs increase year-over-year as your life expectancy decreases (more on how RMDs work in a moment).
  • Other taxable income: Additional sources of taxable income include non-retirement investment income, business earnings and taxable Social Security benefits.
  • Income-related Medicare surcharges: A high income may trigger higher Medicare premiums, adding to your monthly expenses.

How Are 401(k) Withdrawals Taxed?

How do the pieces fit? When you retire, all the money you withdraw from traditional 401(k) and IRA accounts is taxed as ordinary income—the same as your wages are during your working years. You're subject to the same marginal tax rates and tax brackets, but a few new rules come into play.

Estimating RMDs

To encourage retirement account holders to use (and finally pay taxes on) their retirement funds, the IRS requires account holders to begin taking minimum distributions starting April 1 of the year after they either retire or turn 72 (or 73 if you turn 72 after December 31, 2022).

The amount you pay as an RMD is based on average life expectancy: At 73, for example, the IRS estimates your remaining life expectancy at 26.5 years. To estimate your RMD, divide your retirement account balance by your life expectancy.

The IRS has worksheets that help you estimate your RMDs by age. Here's an example of how it might work.

Say you earn $150,000 a year. You've saved aggressively for retirement and your investments have done well. You have $2.5 million in a 401(k) and another $1 million in a traditional IRA. If you retire as a single person at 72 with $3.5 million in retirement, you'll have to take a RMD of $132,075 in your first year of retirement (at age 73). Assuming your money grows at 6% annually, by age 80 your RMD could be nearly $196,000, placing you in the 32% tax bracket—versus the 24% you paid as a working person. In this scenario, your RMD could peak around age 97, when you may be required to take nearly $375,000 from your account, provided you stick to minimum withdrawals and continue to earn 6% on your funds.

Failing to withdraw the required minimum could result in up to a 50% penalty from the IRS.

Taking Stock of Additional Income

Unless your retirement accounts are your only source of retirement income, your tax liability doesn't stop there. Your taxable income may also include:

  • Investment income—capital gains, dividends and interest
  • Earnings or self-employment income
  • Business income
  • Gains from the sale of property
  • Up to 85% of your Social Security benefits, if your income exceeds $34,000 as a single filer or $44,000 as a married couple

Factoring in Medicare Costs

High-income retirees may also be required to add an income-related monthly adjustment amount, or IRMAA, to their Medicare Part B and Medicare prescription drug premiums. If your most recent modified adjusted gross income (MAGI) shows you've made more than $194,000 as a married couple or $97,000 as an individual filer, you may be subject to higher premiums, based on a sliding scale.

For perspective, individuals with a MAGI of $500,000 or more, or married couples with $750,000 or more, would pay an additional $395.60 per month for Medicare Part B and an added $76.40 per month for prescription coverage.

How to Minimize Your Taxes in Retirement

For retirement super-savers, meeting with a retirement financial planner or tax advisor (or both) can be a good place to start. A qualified pro can help you navigate tax laws and investment strategies so you can maximize the money you get to enjoy in retirement—and minimize your tax bill, even if you can't eliminate taxes entirely.

Here are a few tactics that may help you defuse a ticking tax bomb.

Start Saving in a Roth

If you're still mid-career, consider funneling some of your retirement savings into Roth accounts instead of tax-deferred traditional IRAs and 401(k)s. Though you won't get the same tax savings now, your money will grow tax-free in your account and won't be included in taxable income when you withdraw it. Roth IRAs do not have RMDs and, starting in 2024, neither will Roth 401(k)s.

Consider Converting to a Roth

You can roll funds from a traditional IRA or 401(k) into a Roth IRA or 401(k), but your rollover will be taxed as regular income in the year you make the transaction. Weigh the pros and cons of converting all or some of your traditional retirement assets to a Roth.

Save Money in a Health Savings Account

If you have a qualifying high-deductible health plan, consider maxing out your contributions to a health savings account (HSA).

Although HSA funds may only be used to pay for qualifying health care expenses (including medical copays and deductibles, dental expenses and vision care), these expenses can be substantial in retirement. Fidelity's 2023 Retiree Health Care Cost Estimate found that a 65-year-old retiring in 2023 can expect to spend an average of $157,500 in health care and medical expenses throughout retirement.

HSAs have unique tax benefits for retirement savers: You'll get a tax deduction when you contribute to an HSA and won't be taxed on your withdrawals—as long as they're used to pay for qualifying health care expenses.

Think About Your Beneficiaries

Even death may not defeat your tax liability when you leave behind funds in a traditional IRA or 401(k). Non-spousal beneficiaries (like your adult children) have 10 years to distribute inherited IRA or 401(k) funds. These distributions are taxable, unless the money is in a Roth. If your estate's value exceeds $12.92 million in 2023, your heirs may also owe federal and state estate taxes.

Ask your financial advisor for strategies that may help ease the tax burden for your heirs. You may want to convert some funds to a Roth or consider life insurance that helps to cover the cost of taxes.

Meet With a Retirement Planner

Your retirement tax bill has many moving parts: 401(k) distributions, Roth and traditional IRA withdrawals, investment income, Social Security, Medicare surcharges and more. An investment advisor can help you find ways to manage your funds to minimize your tax bill.

The Bottom Line

Although having too much income in retirement beats the opposite problem—having too little—tax considerations in retirement are serious, especially when you have substantial tax-deferred savings set aside. Whether you're currently retired or doing some advance planning, now is a great time to get a handle on your post-retirement taxes. Finding out what your tax liability is likely to be, exploring ways to minimize your tax bill and mapping out ways to pay can help make a retirement tax bomb less explosive.