The Retirement Tax Mistake That Could Cost You Hundreds of Thousands

You spent decades saving for retirement. But have you thought about how much of that money you'll actually keep after taxes?

For many people approaching retirement, the biggest financial concern is whether they've saved enough. They look at their 401(k), IRA, investment accounts, and Social Security benefits and wonder whether their money will last.

But there's another question that deserves just as much attention:

How much will you pay in taxes throughout retirement—and could some of those taxes have been avoided with better planning?

One of the most overlooked retirement planning mistakes is waiting until required minimum distributions (RMDs) begin before developing a tax strategy.

By then, some of the most valuable planning opportunities may have already passed.

The good news? If you're approaching retirement, or even if you've already retired, there may still be opportunities to make your retirement income more tax-efficient.

Let's look at why retirement taxes can become so expensive, how different income sources interact, and what you can do to plan ahead.

Why Retirement Taxes Can Be Higher Than You Expect

Many retirees assume their taxes will decrease once they stop working.

And sometimes they do.

Without a regular paycheck, you may initially find yourself in a lower income tax bracket. But that doesn't necessarily mean you'll remain there throughout retirement.

As you get older, several income sources may begin overlapping:

• Withdrawals from traditional IRAs and 401(k)s

• Required minimum distributions

• Social Security benefits

• Pension income

• Interest, dividends, and capital gains

• Income from rental properties or other investments

Each of these can affect your tax situation differently.

And when they begin overlapping, you may discover that your retirement income creates a larger tax bill than you anticipated.

This is why retirement planning shouldn't focus only on how much you've accumulated. It should also consider how and when you'll use that money.

The Hidden Tax Mistake: Waiting Too Long to Plan

One of the biggest opportunities in retirement tax planning comes down to timing.

Many people experience a period after they stop working but before Social Security benefits and required minimum distributions begin.

During these years, their taxable income may be significantly lower than it was during their working years—and potentially lower than it will be later in retirement.

We often refer to these as the retirement tax planning window, or the gap years.

Imagine someone who retires at 62.

Their salary stops, but they decide to delay Social Security. They also haven't reached the age when required minimum distributions begin.

For several years, they may have greater flexibility over how much taxable income they recognize.

That flexibility creates opportunities to evaluate Roth conversions, retirement account withdrawals, investment gains, and other tax planning strategies.

But if they simply leave their retirement accounts untouched until RMDs begin, they may miss an opportunity to manage their lifetime tax liability.

The mistake isn't necessarily saving too much in tax-deferred accounts.

It's failing to plan for how those accounts will eventually be taxed.

What Happens When Required Minimum Distributions Begin?

Required minimum distributions are mandatory withdrawals from certain retirement accounts, including traditional IRAs and most traditional 401(k)s.

Under current law, RMDs generally begin at age 73 for individuals born from 1951 through 1959 and age 75 for those born in 1960 or later.

The IRS determines the minimum withdrawal using your account balance and an applicable life expectancy factor.

Here's the important part:

You may be required to withdraw money even if you don't need it to cover your living expenses.

And because most traditional retirement accounts were funded with pre-tax dollars, those withdrawals are generally subject to ordinary income taxes.

An Example: $2 Million in Retirement Accounts

Let's say a retired couple has accumulated $2 million in traditional IRAs and 401(k)s.

Assume, for illustration, that the entire $2 million is subject to one account owner's RMD calculation at age 75.

Using the IRS Uniform Lifetime Table's age-75 distribution factor of 24.6:

$2,000,000 ÷ 24.6 = approximately $81,301

That's more than $81,000 in required distributions for the year, assuming the relevant prior year-end balance is $2 million.

And that's before considering Social Security, pensions, investment income, or any other taxable income.

If the couple doesn't need the full distribution to support their lifestyle, they may still have to recognize that income for tax purposes.

Over time, required distributions may become larger as life expectancy factors decrease, although actual amounts will also depend on investment performance and account balances.

This is where tax planning becomes especially important.

The Retirement Tax Stack: RMDs, Social Security, and Medicare

One of the reasons retirement taxes can be difficult to anticipate is that different income sources can affect one another.

We think of this as the retirement tax stack.

1. Required Minimum Distributions Increase Taxable Income

As we just discussed, RMDs can add significant taxable income to your return.

That income may push some of your earnings into a higher marginal tax bracket, depending on your other income and deductions.

But the impact doesn't necessarily stop there.

2. More of Your Social Security Benefits May Become Taxable

Many retirees are surprised to learn that Social Security benefits aren't always tax-free.

Depending on your combined income, up to 85% of your Social Security benefits may be included in your federal taxable income.

That doesn't mean you're paying an 85% tax rate on Social Security.

It means up to 85% of your benefits may be subject to income tax at your applicable rates.

Traditional IRA withdrawals, pension income, and other sources of income can influence how much of your Social Security is taxable.

This creates another reason to consider the timing of retirement account withdrawals.

3. Higher Income Can Increase Medicare Premiums

Medicare introduces another consideration.

Higher-income retirees may pay additional premiums for Medicare Part B and Part D through the Income-Related Monthly Adjustment Amount (IRMAA).

Medicare generally uses income information from two years earlier to determine whether these surcharges apply.

That means a large taxable withdrawal or Roth conversion today could potentially increase your Medicare premiums two years from now.

When required distributions, Social Security taxation, and Medicare surcharges interact, the combined cost can be more significant than retirees expect.

And because these expenses appear in different places—tax returns, retirement distributions, and Medicare premiums—it's not always obvious how closely they're connected.

Could Poor Retirement Tax Planning Really Cost $400,000?

You've probably seen headlines suggesting that retirement tax mistakes can cost hundreds of thousands of dollars.

Is that possible?

Yes, depending on the household's circumstances, account balances, future tax rates, investment returns, withdrawal decisions, and retirement timeline.

But there's an important distinction:

A $400,000 difference is a possible illustrative scenario—not a universal cost or a guaranteed amount of tax savings.

To establish a figure like that for a particular household, you would need to compare two detailed retirement projections using consistent assumptions.

For example:

Scenario A: No Coordinated Tax Strategy

A couple retires with substantial traditional retirement account balances.

They delay taking withdrawals, make no Roth conversions, and begin taking required distributions when mandated.

As their taxable income increases, they may experience higher marginal tax rates, increased Social Security taxation, and Medicare premium surcharges.

Scenario B: Proactive Retirement Tax Planning

The same couple evaluates their expected lifetime tax liability before retiring.

They consider partial Roth conversions during lower-income years, coordinate withdrawals from different account types, and plan around Social Security and Medicare.

They may pay more taxes in certain earlier years to reduce taxes later.

The difference between these approaches can become meaningful over a retirement lasting 20 to 30 years.

However, proactive strategies aren't automatically better. The outcome depends on the taxes paid upfront, future tax rates, investment performance, Medicare effects, and other household-specific factors.

The goal isn't to avoid paying taxes altogether.

It's to avoid paying more over your lifetime than necessary.

Strategy #1: Consider Roth Conversions Before RMDs Begin

One retirement tax planning strategy worth evaluating is a Roth conversion.

A Roth conversion involves moving money from a traditional IRA or eligible retirement account into a Roth IRA.

The amount converted is generally included in taxable income to the extent it hasn't already been taxed.

Why would someone voluntarily pay taxes today?

Because qualified Roth IRA withdrawals can be tax-free, and Roth IRAs don't require minimum distributions during the original owner's lifetime.

For someone expecting higher taxable income later in retirement, converting some traditional retirement savings during lower-income years may create long-term benefits.

Why Partial Roth Conversions May Make Sense

The goal usually isn't to convert your entire traditional IRA at once.

A large conversion could create a substantial tax bill and potentially affect other income-related costs.

Instead, a financial planner might evaluate whether converting a smaller amount each year makes sense.

For example, someone might consider converting enough to use a portion of their available tax bracket without unnecessarily pushing additional income into a higher bracket.

This is sometimes called filling the tax bracket.

But Roth conversions aren't appropriate for everyone.

Before converting, consider:

• Your current tax bracket versus expected future tax brackets

• How you'll pay the taxes on the conversion

• Your retirement income needs

• Medicare IRMAA thresholds

• Social Security taxation

• State income taxes

• Your estate and beneficiary goals

• How long the converted money may remain invested

A Roth conversion should be evaluated as part of a long-term retirement plan, not simply because someone says Roth accounts are better.

Strategy #2: Be Intentional About Which Retirement Accounts You Withdraw From

Another important retirement planning decision is determining where your income will come from each year.

Many retirees accumulate money across several types of accounts.

Taxable Brokerage Accounts

These may contain investments purchased with after-tax dollars.

Withdrawals aren't automatically taxed in full. Instead, taxes may arise from realized capital gains, interest, dividends, and other taxable activity.

Traditional IRAs and 401(k)s

These accounts generally provide tax-deferred growth, but distributions of previously untaxed amounts are typically taxed as ordinary income.

Roth IRAs

Qualified withdrawals from Roth IRAs are generally tax-free, providing another potential source of retirement income.

Having money across different account types can create flexibility.

For example, in a year when taxable income is already relatively high, taking qualified Roth withdrawals may help avoid adding more ordinary income.

In another year, it may make sense to intentionally withdraw from a traditional IRA to take advantage of a lower tax bracket.

There's no single withdrawal order that's best for every retiree.

The right strategy depends on your assets, income, tax situation, and long-term goals.

This is why we believe retirees should have a retirement income plan that shows where their money will come from year after year, rather than making withdrawal decisions one account at a time.

Strategy #3: Coordinate Social Security With Your Retirement Income Plan

Social Security is another important piece of the retirement tax puzzle.

The age at which you begin claiming benefits can affect both your monthly income and the taxes you pay throughout retirement.

Some retirees begin benefits at 62, while others delay until full retirement age or as late as age 70.

There are several factors to consider, including:

• Your expected longevity

• Your spouse's benefits

• Your retirement spending needs

• Your investment assets

• Your income tax situation

• Potential survivor benefits

Delaying Social Security may create a period when you have more flexibility to recognize income from other sources.

For some retirees, that can create opportunities to evaluate Roth conversions or traditional IRA withdrawals before Social Security income begins.

But delaying isn't automatically the right choice.

A coordinated retirement plan should evaluate both the income benefits and the tax consequences of different claiming strategies.

Strategy #4: Don't Overlook Year-End Tax Planning

One of the simplest ways to improve your retirement planning process is to stop waiting until tax season to discuss taxes.

When you meet with your CPA in April, most of the previous year's financial decisions have already been made.

Tax preparation tells you what happened.

Tax planning helps you determine what to do next.

Before December 31, consider reviewing:

• Your projected taxable income for the year

• Potential Roth conversion opportunities

• Realized capital gains and losses

• Required minimum distributions

• Charitable giving strategies

• Retirement account withdrawal needs

• Investment income

• Estimated tax payments and withholding

Some strategies have different deadlines and eligibility requirements, so they should be reviewed individually.

And remember, tax planning shouldn't happen in isolation.

Your financial advisor and CPA should understand how the decisions being made in one area may affect the others.

What If You're Already Retired and Taking RMDs?

If your required minimum distributions have already started, you haven't necessarily missed every opportunity.

You may still benefit from reviewing:

Tax-efficient withdrawal strategies. Coordinating withdrawals across taxable, traditional, and Roth accounts may help manage annual taxable income.

Qualified charitable distributions. Eligible IRA owners age 70½ or older may be able to make qualifying charitable gifts directly from their IRA, potentially satisfying all or part of an RMD while excluding the qualifying distribution from income.

Roth conversions. Depending on your situation, conversions may still be worth evaluating after RMDs begin, although the year's required distribution itself cannot be converted.

Investment tax efficiency. Asset location, capital gains management, and portfolio structure can influence taxes throughout retirement.

Medicare premium planning. Understanding IRMAA thresholds and income timing may help avoid unnecessary surprises.

Even when certain opportunities have passed, there may still be meaningful decisions you can make.

Three Questions to Ask Before Retirement

If you're within five years of retirement, now is an excellent time to begin evaluating your retirement tax strategy.

Start with these three questions.

1. When Will My Taxable Income Change?

Identify when your employment income will stop, when Social Security benefits may begin, and when required minimum distributions will be required.

Look for years when your taxable income may be lower than usual.

2. How Much of My Retirement Savings Is in Pre-Tax Accounts?

If a large percentage of your retirement savings is held in traditional IRAs or 401(k)s, future distributions could have a significant impact on your tax situation.

Understanding that exposure today may create more flexibility in planning for tomorrow.

3. Do I Have a Strategy for Lifetime Taxes?

Rather than focusing exclusively on reducing this year's tax bill, ask whether your current strategy considers taxes over your entire retirement.

Sometimes paying a little more in taxes today may help reduce a much larger liability later.

Other times, deferring taxes may be the better decision.

The important thing is understanding the tradeoffs before making the decision.

Retirement Planning Should Help Your Money Last—and Support the Life You Want to Live

At Fit Wealth, we believe retirement planning is about more than reaching a certain investment balance.

It's about understanding how your investments, taxes, income, and long-term goals work together.

You've spent years building your wealth.

Now the focus shifts to making thoughtful decisions about how to use it.

Whether that means traveling more, spending time with family, pursuing new interests, staying active, or simply having the option to stop working, your financial plan should support the life you want to live.

And the more intentional you are about retirement taxes, the better positioned you may be to make the most of what you've built.

Because successful retirement planning isn't just about how much money you've saved. It's also about how much you can keep, how you use it, and how long it needs to last.

Want to Know Whether Your Retirement Tax Strategy Is on Track?

If you're approaching retirement or already retired, now may be a good time to review how your retirement accounts, Social Security benefits, and tax strategy work together.

At Fit Wealth, we help individuals and families make informed decisions about their investments, retirement income, and long-term financial planning.

Introduce yourself at www.fitwealthadvisors.com.

We'd love to learn more about your financial goals and what you're planning for in the years ahead.

Listen to The Fit Wealth Show

For more on this topic, listen to our episode, The Hidden Tax Mistake That Could Cost Retirees $400,000 (And How to Avoid It), with Amanda and Shawn Hanquist.

You can also watch our retirement tax planning discussion on YouTube.

This article is for educational and informational purposes only and is not intended as individualized investment, tax, or legal advice. Tax strategies depend on individual circumstances and applicable laws. Examples are hypothetical and do not represent actual client results or guaranteed savings. Consult qualified financial and tax professionals before implementing any strategy.