The Roth Conversion Window Between Retirement and RMDs

For many retirees, there is a stretch of years that tax planners quietly consider the most valuable of an entire financial life: the gap between the final paycheck and the first required minimum distribution. Wages have stopped. Social Security may not have started. Required withdrawals from pre-tax accounts have not yet begun. For a household that spent decades in the 24% bracket or above, taxable income in these years can fall dramatically — and that is precisely what makes them interesting.

A Roth conversion moves money from a pre-tax retirement account, such as a traditional IRA or 401(k), into a Roth IRA. The amount converted is taxed as ordinary income in the year of the conversion. In exchange, the converted dollars — and all future growth on them — are generally free of federal income tax when withdrawn in retirement, provided the account and holding-period rules are met. Converting during high-earning years means paying tax at your peak rates. Converting during the low-income window means the same dollars may be taxed at 10%, 12%, or 22% instead.

The arithmetic that matters is bracket-filling. Each year of the window, there is a certain amount of income that can be recognized before crossing into the next tax bracket. A partial conversion sized to fill — but not exceed — a chosen bracket converts pre-tax dollars at a known, comparatively low rate. Repeated over several years, this can meaningfully shrink the pre-tax balance that will later be subject to required minimum distributions.

Why does shrinking that balance matter? Because RMDs are not optional. Beginning at age 73 (rising to 75 for those born in 1960 or later), the IRS requires annual withdrawals from pre-tax accounts calculated from account balances and life expectancy tables. Large pre-tax balances can force large taxable withdrawals — sometimes pushing retirees into higher brackets than they occupied while working, increasing the taxable share of Social Security benefits, and triggering Medicare income-related premium surcharges (IRMAA).

There are real costs and constraints to weigh. The tax on a conversion is due in the year of conversion, and paying it from the converted funds themselves reduces the amount that reaches the Roth. Conversions raise your modified adjusted gross income, which can affect Medicare premiums two years later and the taxation of Social Security benefits in the conversion year. Each conversion also starts its own five-year clock for penalty-free access to converted principal before age 59½ — less relevant for most retirees, but part of the rules. And a conversion cannot be undone; recharacterization of conversions was eliminated in 2018.

The window is also narrower than it first appears. Claiming Social Security adds income to each year. Pensions, rental income, and capital gains all consume bracket space that might otherwise be used for converting. This is why the decision is rarely "convert or don't" — it is a year-by-year sizing exercise across a specific household's income map, ideally revisited annually as tax law, account balances, and spending plans change.

None of this constitutes a recommendation to convert. For some households — those expecting lower income in later retirement, those planning substantial charitable giving from pre-tax accounts through qualified charitable distributions, or those whose heirs will inherit in low brackets — conversions can be unattractive. The point is narrower: the years between retirement and RMDs are structurally unusual, the opportunity they present is scheduled to expire, and the households that benefit most are the ones that examined the question while the window was still open.