A Untouched 403(b) Grew to $770,000 — Then the IRS Knocked

A teacher who retired at 60 with $410,000 in a 403(b) and lived entirely on her pension left the account untouched for 13 years; by 73 it had reached $770,000 and her first required minimum distribution was $29,000 of taxable income stacked on top of her pension.

She did everything the conventional advice says to do. She retired at 60 with $410,000 in a 403(b), the workplace retirement plan used by public school, hospital and nonprofit employees. Her pension covered the mortgage, the groceries, the car insurance and the trips. So she never touched the retirement account. For 13 years it sat there, compounding, untouched and untaxed.

By 73 it had grown to $770,000. That is the part of the story that looks like a win. The part that did not look like a win arrived in the form of her first required minimum distribution: $29,000 of forced taxable income, stacked directly on top of a pension that was already filling her tax brackets from the bottom up.

Why a Bigger Balance Became a Tax Problem

A 403(b), like a traditional 401(k) or IRA, is tax-deferred, not tax-free. Every dollar that went in escaped income tax in the year it was earned, and every dollar of growth on top of it has been compounding on a deferred basis. The bill was never cancelled. It was postponed — and the balance that the IRS eventually taxes is the balance after all that growth.

That is the mechanical trap. Growing the account from $410,000 to $770,000 over 13 years meant adding roughly $360,000 of value, an increase of about 88% — and it also meant enlarging the base on which required minimum distributions are calculated. RMDs are the annual withdrawals the tax code forces out of tax-deferred accounts once a retiree reaches the applicable age. The government waited patiently for its share. It did not waive it.

Her first RMD of $29,000 works out to roughly 3.8% of the $770,000 balance. That percentage is not fixed. It climbs each year as life expectancy shortens, which means that unless markets fall hard, the forced withdrawal grows in both dollar terms and as a share of what remains. The first RMD is almost always the smallest one a retiree will ever take.

The Pension Filled the Low Brackets First

Here is what made her situation different from a retiree without a pension. Between 60 and 73, her pension income was already being taxed. It occupied the standard deduction and the lowest brackets. So when the $29,000 RMD arrived, it did not start at zero — it landed on top, taxed at her marginal rate, the rate that applies to the last dollar of income rather than the average across all of it.

During those same 13 years, she had what planners call a low-bracket window that she never used. She could have drawn modest amounts from the 403(b) each year, paid tax on them at whatever rate the pension left available, and reduced the balance that would later be force-fed into her return. Alternatively, she could have executed Roth conversions — moving money from the tax-deferred 403(b) into a Roth account, paying the income tax up front, and permanently removing those dollars from future RMD calculations. Roth accounts have no lifetime required distributions for the original owner.

Doing nothing felt like discipline. Functionally, it was a decision to concentrate 13 years of tax liability into a period when she had the least flexibility to manage it.

Medicare Surcharges and the Social Security Squeeze

The income tax is only the visible part. Two other systems read the same income figure and respond to it.

• Medicare premiums. Part B and Part D premiums are income-tested through a surcharge known as IRMAA — the income-related monthly adjustment amount. It is assessed on modified adjusted gross income, and it works on cliffs rather than a smooth slope. Cross a threshold by a small margin and the full surcharge tier applies for the year. A $29,000 RMD dropped onto pension income is exactly the kind of addition that pushes a retiree over a line she did not know she was near.
• Social Security taxation. The share of a Social Security benefit that becomes taxable depends on a combined-income calculation that includes RMD dollars. Retirees who assumed their benefit would arrive largely intact often discover that a large forced withdrawal drags a much bigger portion of it into taxable territory. That is the Social Security she "never expected to lose," as the case was described by 24/7 Wall St.

There is also a lag worth understanding: IRMAA determinations generally look back at a tax return filed two years earlier. A retiree can therefore take a large distribution one year and feel the Medicare consequence well after the money has already been spent, with no obvious connection between cause and effect.

Markets Made the Balance, and Markets Can Unmake the Plan

A balance that nearly doubles over 13 years is, in large part, a function of what equities did during the holding period. That cuts both ways. RMDs are calculated on the prior year-end balance, so a retiree who is forced to withdraw into a falling market sells assets at depressed prices to satisfy a distribution sized by a higher valuation.

For context on where broad markets sit, the S&P 500 tracker SPY closed at $761.69 on Friday, 18 September 2026, down 0.12% on the day, while the Nasdaq 100 fund QQQ finished at $721.45, up 0.63%, and the Dow tracker DIA ended at $515.88, down 0.48%. Balances built on those indexes are marked to whatever the market delivers — the RMD schedule is not.

The Window That Closes Quietly

The practical lesson is that the gap between retirement and RMD age is the single most valuable tax-planning period most retirees will ever have, and it is easiest to waste when income needs are already covered. Someone with a pension, or a large cash cushion, or a spouse still working has the least immediate reason to touch a tax-deferred account — and therefore the most to gain from touching it deliberately.

A few questions worth answering before that window shuts:

• How much room is left in the current bracket after pension and any other fixed income, and could that room absorb a partial Roth conversion each year?
• Where do the IRMAA thresholds sit relative to projected income, remembering the two-year lookback?
• What does the tax-deferred balance look like projected forward to RMD age, and what distribution does that imply?
• For a married couple, what happens to the survivor, who will face those same distributions under single filer brackets?

None of this makes the $770,000 a failure. She has more money than she started with, and considerably more than she would have had by spending it down early. But the difference between a well-managed drawdown and a deferred one shows up not in the balance — it shows up in how much of that balance she actually keeps, and in how many adjacent systems quietly reprice her retirement because of a single line on a tax return.

Frequently asked questions

What is a required minimum distribution?

A required minimum distribution, or RMD, is the amount the tax code forces you to withdraw each year from tax-deferred retirement accounts such as a 403(b), traditional 401(k) or traditional IRA once you reach the applicable age. The withdrawal is treated as ordinary taxable income. Roth accounts have no lifetime RMD requirement for the original owner.

Why did leaving the 403(b) untouched cost her money?

Because her pension already filled the lower tax brackets, the eventual $29,000 RMD was taxed at her top marginal rate rather than at low rates. Drawing modest amounts between ages 60 and 73, or converting some to a Roth account, would have used lower-bracket room each year and shrunk the balance later subject to forced distributions.

What is IRMAA and how does an RMD trigger it?

IRMAA is the income-related monthly adjustment amount, a surcharge added to Medicare Part B and Part D premiums for higher-income enrollees. It is assessed in tiers with hard thresholds, so crossing a line by a small amount triggers the full tier. A large RMD added to existing income can push a retiree over a threshold unexpectedly.

How can an RMD affect Social Security taxation?

The portion of a Social Security benefit that is taxable depends on a combined-income calculation that includes distributions from tax-deferred accounts. A large RMD raises that combined income and can push a substantially bigger share of the benefit into taxable territory, reducing the net amount a retiree keeps even though the gross benefit is unchanged.

What is a Roth conversion window?

It is the period, usually between retirement and the start of required distributions, when taxable income is temporarily low and a retiree can move money from a tax-deferred account into a Roth, paying income tax at a lower rate. Converted dollars are removed from future RMD calculations permanently for the original account owner.

Does the first RMD stay the same each year?

No. The required percentage rises as life expectancy factors shorten, so the distribution typically grows both in dollars and as a share of the account unless markets fall significantly. The first RMD is generally the smallest one a retiree will take, which is why planning before it begins matters more than reacting afterwards.

Sources

• She Retired at 60 With $410,000 in a 403(b) and Lived on Her Pension for 13 Years. By 73 It Was $770,000, and Her First RMD Was $29,000, on Top of the Pension — 24/7 Wall St