One of the most powerful yet underused retirement planning moves is converting portions of a Traditional IRA to a Roth IRA during the years when your taxable income is unusually low. These “low-income” years create empty space in the lower federal tax brackets—space you can deliberately fill by triggering conversion income at today’s known tax rates rather than being forced into much higher brackets later when Required Minimum Distributions (RMDs) begin.

RMDs and Tax Brackets

RMDs currently start at age 73 (75 for those born in 1960 or later) and are calculated based on your prior-year-end Traditional IRA balance divided by an IRS life-expectancy factor. Because RMDs are treated as ordinary income and added on top of Social Security, pensions, or other income, they frequently push retirees from the 12% or 22% bracket into the 22%, 24%, or even 32% bracket—sometimes permanently. Once RMDs are large enough, every additional dollar of Traditional IRA withdrawal or growth is taxed at these higher marginal rates for the rest of your life (and your spouse’s life). A Roth conversion done earlier avoids this trap because Roth distributions (including all future growth) are tax-free.

The Roth IRA Conversion Window

The ideal conversion window typically occurs in the years between retirement and the start of RMDs/Social Security. Common scenarios include:

1. Early retirement (50s to early 60s) before claiming Social Security or pensions.
2. The gap years after leaving a high-paying job but before age 73.
3. Years when you have large deductions (charitable giving, medical expenses, or business losses) that artificially lower taxable income.
4. Widowhood years, when a surviving spouse temporarily files as single in a lower bracket before Social Security survivor benefits or RMDs kick in.

In these periods, you can convert just enough each year to “top off” the 12% or 22% bracket (or even the 24% bracket if rates are favorable). For 2025, a married couple filing jointly can have up to roughly $94,300 of taxable income and still stay in the 12% bracket, and up to $201,050 in the 22% bracket. Converting $80,000–$100,000 per year during low-income years at 12–22% often beats paying 24–37% (or higher under potential future law changes) later.

Tax Savings

The math is compelling. Suppose a 62-year-old couple has $1.2 million in Traditional IRAs and expects $90,000 of combined Social Security/pension income. By age 73 their RMD alone could exceed $60,000 and grow every year, pushing them into the 22–24% brackets indefinitely. Converting $100,000 annually for six years (2025–2030) at an average effective rate of ~18% costs roughly $108,000 in total tax but eliminates ~$500,000–$800,000 of future taxable RMDs that would have been taxed at 24%+. The breakeven is usually 8–12 years; after that, the Roth owner (or heirs) come out far ahead.

The Bottom Line

The longer you wait, the narrower the window becomes and the larger each conversion must be to move the needle—driving you into higher brackets today instead of lower ones. Once RMDs start, the opportunity largely disappears. Proactive, multi-year conversions in the lower-bracket years are therefore one of the few irreversible tax-planning decisions that can permanently reduce lifetime taxation for you and your heirs. Waiting until “you need the money” or “tax rates go up” is usually the most expensive mistake of all.