He Converted $40,000 a Year for Ten Years. His Brother Left the Same $450,000 Alone and Watched It Grow to $730,000. Only One of Them Owns What the Statement Says

Two brothers, same starting balance of $450,000 in a traditional IRA, same age, same market. Imagine that one spent a decade moving $40,000 a year into a Roth, paying tax on each conversion at the 12% federal rate. The other brother did nothing and watched the balance climb to $730,000. On paper, the second brother looks like he came out ahead. In practice, he owns less of what his statement says than his brother owns of a smaller one.

Why the Statement Includes the Government’s Share

A traditional IRA balance is money on which no federal income tax has ever been paid. Every dollar withdrawn is taxed as ordinary income in the year it comes out. If the eventual tax rate is 22%, then twenty-two cents of every dollar on that statement belong to the Treasury. The account holder is a custodian for a share he does not own.

A Roth statement works differently. Tax has already been settled. Qualified withdrawals in retirement come out untaxed. The number on the page is the number the owner can spend. Two brothers whose statements read the same figure do not have the same wealth if one is a Roth and the other is pre-tax. Almost no one adjusts for this when deciding whether they have enough saved.

Building the Comparison Fairly

The scenario here between the two brothers assumes a mid-single-digit annual return, conversion tax paid at 12% from money held outside the retirement account, and an eventual withdrawal rate of 22% for the brother who never converted. Under those assumptions, the converter ends the ten-year stretch with a Roth balance that spends dollar for dollar, while the non-converter’s larger statement is worth what remains after the government takes its share on the way out.

The converter also gave something up. A decade of writing checks to the IRS meant a decade of not investing that same money elsewhere. That opportunity cost is real, and it’s why paying conversion tax from outside the account matters. Using IRA dollars to pay the tax defeats the strategy.

When the Bet Can Go the Other Way

Conversion is a bet that the rate paid now is lower than the rate paid later. If the non-converting brother lives on modest income in retirement, with required distributions that stay inside the two lowest brackets, he may pay less than the 12% his brother paid up front. In that case, the non-converter comes out ahead.

Who is genuinely in that position? Someone with a small pre-tax balance, no pension, and Social Security as the majority of household income. For that retiree, doing nothing is often the correct answer.

Where the Converter’s Advantage Does Not Depend on Rates

Several benefits hold regardless of future brackets. Roth IRAs carry no lifetime required distributions for the original owner, so the converter is never forced to realize income he does not need. The non-converter’s mandatory withdrawals raise the modified adjusted gross income that determines how much of his Social Security is taxable and whether he pays Medicare Part B and Part D income-related premium surcharges, which use a two-year lookback on that same figure.

Heirs inherit the difference too. Under current rules, a traditional IRA passed to an adult child is generally emptied within ten years, and every dollar is taxed at the heir’s marginal rate, often during peak earning years. A Roth inherited under the same window comes out tax-free.

Bracket Mechanics That Make Low-Rate Conversions Possible

The strategy depends on filling low brackets before higher ones apply. For tax year 2026, the 12% rate begins at income above $12,400 for a single filer. A retiree with little other taxable income can measure how much room remains beneath the next bracket and convert into that space each year. The standard deduction sits underneath that structure, sheltering the first slice of income before any bracket applies. The quiet stretch between the last paycheck and the first required distribution is often the cheapest tax environment a retiree will see again, and we sized up that window in a free guide: The Roth Window.

Adjustments to Make Before Deciding You Have Enough

A traditional IRA or 401(k) statement reduced by the tax rate expected on withdrawals in retirement leaves the balance that actually belongs to the account holder. The gap between the printed number and the after-tax number is often the difference between retiring comfortably and retiring close to the edge. The brother whose statement reads larger may own less. The one who paid the tax already knows exactly what he has.

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