For many retirees, there's a short stretch of years, often five to ten, that passes with surprisingly little attention. The paycheck has stopped. Social Security may not have started yet, or hasn't been claimed. Required minimum distributions (RMDs) from traditional retirement accounts are still years away. Taxable income, for a brief window, can be lower than it has been in decades, and lower than it may ever be again.
This stretch is sometimes called the Roth conversion window, and for pre-retirees and recent retirees with significant pre-tax retirement assets, it can be one of the more meaningful tax-planning opportunities of a lifetime. It isn't a guarantee of lower lifetime taxes for every household, and it isn't right for everyone. But understanding how it works, and why timing matters so much, is worth a closer look.
Key takeaways
- The Roth conversion window is the period between retirement and the start of RMDs, when taxable income is often temporarily lower.
- Converting traditional IRA or retirement plan assets to a Roth IRA during these lower-income years means paying tax on the conversion now, often at a lower rate than you might pay later.
- Partial, multi-year conversions (bracket filling) are a common approach, rather than converting a large balance all at once.
- Conversions can affect Social Security taxation and Medicare premiums (IRMAA), so timing and amount both matter.
- A Roth conversion strategy should be evaluated as part of a broader, personalized plan, not as a one-size-fits-all tactic.
What Is the Roth Conversion Window?
What is a Roth conversion window? It's the span of years after you stop earning a full-time paycheck but before you're required to begin taking RMDs from traditional IRAs or employer retirement plans. Under current federal rules, RMDs generally begin at age 73, with the applicable age rising to 75 for individuals born in 1960 or later, so the window often runs through the early-to-mid retirement years (IRS RMD FAQs).
During this period, a retiree's taxable income can drop meaningfully. Wages have ended. Social Security may be delayed to increase future benefits. Pension income may not have started. RMDs, which eventually force taxable withdrawals whether or not the money is needed, haven't kicked in. That combination can create a temporary dip in taxable income, and a temporary dip in your marginal tax bracket, that won't necessarily last.
When should retirees consider a Roth conversion?
Generally, a Roth conversion is worth evaluating in years when taxable income is lower than it's expected to be later in retirement, particularly once RMDs and Social Security are both layered in. The goal is not to eliminate taxes, since a conversion is a taxable event in the year it's completed, but to potentially pay tax on that income at a lower rate than you might face in the future (IRS Retirement Plans FAQs Regarding IRAs).
Why the Years Before RMDs Matter
Once RMDs begin, the IRS requires you to withdraw a minimum amount from traditional accounts each year, and that income is taxable whether you need it or not. Importantly, once an RMD applies, that year's RMD must be fully distributed before any additional funds can be converted, and the RMD itself can never be converted to a Roth (IRS Publication 590-A). In other words, once the window closes, your flexibility narrows. The years before RMDs start are often the only time you have real control over how much taxable income shows up on your return.
Managing Your Tax Bracket With Partial Conversions
Few retirees convert an entire IRA at once, and for good reason: converting too much in a single year can push income into a higher bracket, erasing much of the benefit. Instead, many households use a strategy sometimes called bracket filling, converting just enough each year to use up the room remaining in a target tax bracket without spilling into the next one.
This typically means:
- Estimating total taxable income for the year, including any pension, interest, dividends, and part-time income.
- Identifying how much room remains before the next bracket threshold.
- Converting an amount designed to use that remaining room, often repeated over several years rather than done all at once.
Because there is no income limit on who can convert traditional retirement assets to a Roth, this strategy is available regardless of household income, even though direct Roth IRA contributions are income-restricted (IRS Publications on IRAs).
The Ripple Effects: Social Security and Medicare IRMAA
A Roth conversion doesn't exist in isolation. The additional income it creates in a given year can also affect:
- Social Security taxation. Depending on total combined income, a larger conversion can increase the portion of Social Security benefits subject to federal income tax.
- Medicare premiums. Under Medicare's Income-Related Monthly Adjustment Amount (IRMAA) rules, premiums for Part B and Part D are generally based on income reported roughly two years earlier. A large conversion today could mean higher Medicare premiums a couple of years down the road.
Neither of these effects necessarily rules out a conversion, but they're exactly why the size and timing of a conversion deserve careful modeling rather than a rule of thumb.
Tax-Rate Uncertainty and the Case for Diversification
No one can predict with certainty what tax rates will look like in ten or twenty years. That uncertainty is itself an argument some retirees find compelling: by converting a portion of pre-tax assets to Roth over time, you create tax diversification, a mix of taxable, tax-deferred, and tax-free resources to draw from later. That flexibility can be valuable regardless of which direction future tax policy moves.
Estate and Legacy Planning Benefits
Roth IRAs offer two features that matter for legacy planning. First, the original owner has no lifetime RMD requirement, meaning the account can continue growing tax-free for as long as it's held. Second, qualified withdrawals, including those eventually taken by heirs, are generally tax-free. For households focused on passing assets to the next generation, shifting some pre-tax dollars into a Roth during the conversion window can be one way to manage the tax character of what's ultimately inherited.
An Illustrative Example
Consider a hypothetical couple, both 64, who retired this year. Their only taxable income is modest interest and dividend income, since they've delayed Social Security and haven't yet begun RMDs. In a typical year, this leaves meaningful room in their current tax bracket before reaching the next threshold.
Rather than let that bracket room go unused, they convert a portion of a traditional IRA each year for several years, paying the resulting tax from savings outside the IRA so the full converted amount keeps growing tax-free inside the Roth. By the time RMDs would otherwise begin, their traditional balance, and therefore their future required withdrawals, is smaller than it would have been. This is a hypothetical example only, intended to illustrate the mechanics of bracket filling. It does not represent any actual client, and results will vary based on each household's income, tax situation, and goals.
When a Roth Conversion May Not Be the Right Fit
A Roth conversion strategy isn't universally advantageous. It may be less appropriate when:
- You expect to need the converted funds in the near term, since conversions are generally irrevocable.
- A conversion would push you into a substantially higher bracket than you're likely to face later.
- You're charitably inclined and a Qualified Charitable Distribution (QCD) from a traditional IRA might better fit your goals.
- State income tax considerations make a conversion less favorable where you live now or where you plan to retire.
- You have an unusually large deductible expense in the current year, such as significant medical costs, that already lowers your taxable income for reasons unrelated to the conversion window.
Common mistakes to avoid
- Converting a large lump sum without modeling the bracket, Social Security, and IRMAA effects together.
- Using the converted funds themselves to pay the resulting tax bill, which reduces the amount left to grow tax-free.
- Assuming the window is identical for every household; your RMD start age depends on your birth year.
- Treating a conversion decision as a one-time event rather than revisiting it each year as income and tax law change.
When to talk with us
Every household's mix of income, account balances, state residency, and long-term goals is different, and a Roth conversion strategy that makes sense for one retiree may not make sense for another. We don't provide individualized tax advice in isolation, and we can't guarantee future results or predict future tax rates with certainty, but we can help you model how a conversion strategy might fit within your broader retirement income and legacy plan. If the years between retirement and RMDs are approaching for you, it may be worth evaluating whether this window applies to your situation, alongside your tax professional.
Frequently asked questions
What is a Roth conversion window? It's the period between retirement and the start of required minimum distributions, when taxable income is often temporarily lower, creating a potential opportunity to convert traditional retirement assets to a Roth IRA at a lower tax cost.
When should retirees consider a Roth conversion? Generally in years when taxable income is lower than expected in later retirement, particularly before Social Security and RMDs are both being received.
Why are the years before RMDs important? Because once RMDs begin, you lose flexibility: that year's RMD must be withdrawn first, and it cannot itself be converted, which narrows your ability to manage taxable income going forward.
Can Roth conversions reduce future taxes? They may, by shifting taxation of certain assets to a year with a lower marginal rate and by reducing future RMDs, but the actual benefit depends on your specific tax situation and cannot be guaranteed.
What are the risks of Roth conversions? Conversions are generally irrevocable, are taxed as ordinary income in the year completed, and can increase Social Security taxation and Medicare IRMAA surcharges if not carefully sized.