Roth IRA Conversion Strategy: When It Makes Sense and When It Doesn't

Key takeaways

• A Roth conversion is a tax bet. You're comparing your tax rate today against your expected rate later, and the gap between the two is what determines whether it's worth doing.
• The years after retirement but before required minimum distributions begin at 73 are often the lowest-income, lowest-bracket window you'll have, which makes them worth a closer look.
• A conversion large enough to cross a Medicare IRMAA threshold can add over $1,000 a year in premium surcharges, showing up two years later.
• Once you convert, it's permanent. There's no recharacterization option to undo it if your situation or the market changes.

If you have money sitting in a traditional IRA or old 401(k), you already know the government gets a cut eventually. A Roth conversion lets you decide when you pay that tax bill, and sometimes at what rate, instead of leaving the decision to required minimum distributions (RMD) and whatever tax law looks like a decade from now. That flexibility is the appeal, and it's also a risk, because a conversion is a tax event you can't undo once it's done.

This isn't a new idea. Advisors have been recommending Roth conversions for years. What's changed is the math around them, which include 2026 tax brackets, Medicare surcharge thresholds, and required minimum distribution rules all shift the calculations depending on your specific numbers. Here's how to think through whether a conversion fits your situation, and where the strategy tends to go wrong.

What a Roth conversion does

A Roth conversion moves money from a traditional IRA (or an eligible employer plan) into a Roth IRA. The amount you convert gets added to your taxable income for that year, and you pay ordinary income tax on it now. In exchange, that money and everything it earns afterward comes out tax-free in retirement, with no required withdrawals during your lifetime.

There's no income limit on who can convert and no annual cap on how much. A conversion can be done as a direct, trustee-to-trustee transfer, which means it isn't subject to the once-per-12-months limit that applies to indirect IRA-to-IRA rollovers⁽³⁾. You can convert $5,000 or $500,000 in a single year. The only real constraint is how much tax you're willing, or able, to pay in the year you do it.

The entire strategy comes down to one comparison.

Your marginal tax rate today versus your expected marginal tax rate when you'd otherwise withdraw that money. If you convert at a lower rate than you'd eventually pay on required withdrawals, you come out ahead. If you convert at a higher rate, you don't.

For 2026, the federal brackets for single filers are:

• 10% up to $12,400
• 12% up to $50,400
• 22% up to $105,700
• 24% up to $201,775
• 32% up to $256,225
• 35% up to $640,600
• 37% above $640,600

The thresholds roughly double for married couples filing jointly, and the standard deduction is $16,100 for single filers and $32,200 for joint filers in 2026⁽¹⁾.

Here's what that looks like in practice. Let’s say you're single and retired, and your taxable income this year, after the standard deduction, is $70,000. You're sitting in the 22% bracket, which runs up to $105,700. That leaves $35,700 of room before you'd cross into the 24% bracket. Converting an amount up to that threshold keeps every dollar taxed at 22%. Convert more than that, and the excess gets taxed at 24%, still not unreasonable, but it’s important to understand how the tax rate changes.

This is often called bracket filling. Converting exactly enough to use up the room in your current tax bracket without spilling into the next one. It's one of the more common approaches because it caps your downside. You know precisely what rate you're paying, rather than guessing at what a future bracket might look like.

For married couples filing jointly, the same logic applies at wider thresholds.

The 2026 brackets run:

• 10% up to $24,800
• 12% up to $100,800
• 22% up to $211,400
• 24% up to $403,550
• 32% up to $512,450
• 35% up to $768,700
• 37% above $768,700⁽¹⁾

A couple with $150,000 in taxable income sits in the 22% bracket with $61,400 of room before crossing into the 24% bracket. The same bracket-filling logic holds, just with different numbers.

Source: IRS Revenue Procedure 2025-32, tax year 2026⁽¹⁾.

A conversion ladder: spreading it out instead of doing it all at once

Rather than converting a large balance in a single year, some people convert a set amount each year over a five, ten, or even twenty year stretch. Spreading a $400,000 traditional IRA balance across eight years at $50,000 a year, for example, keeps each year's converted amount inside a lower bracket than dumping the full $400,000 into taxable income in one shot, which would push most filers well into the 32 or 35% brackets.

A ladder also gives you flexibility year to year. If your income is unusually high in a given year, perhaps from a large capital gain or a one-time bonus, you can convert less or skip that year entirely. If your income drops, you can convert more. The tradeoff is that a longer ladder means a longer stretch of years where you're paying some tax on the conversion, rather than getting it behind you quickly, and it requires you to actually revisit the calculation every year rather than making one decision and moving on.

When a conversion tends to make sense

The years between retirement and required minimum distributions (RMD) . If you retire before your Social Security and RMDs begin, you may have several years where your taxable income drops significantly, sometimes into the 12 or 22% bracket. That window is often the cheapest opportunity you'll get to convert, because your income later, once RMDs and Social Security stack on top of each other, may put you in a higher bracket than you're in right now.

That's a meaningful consideration, because traditional IRA and 401(k) balances force withdrawals starting the year you turn 73⁽²⁾. RMDs are calculated as a percentage of your prior year-end balance, and they only grow larger as the account continues to compound and the IRS's life expectancy divisor shrinks. For someone with a large pretax balance, RMDs alone can push them into a higher bracket than they've ever been in, whether they want the income or not. Converting some of that balance earlier, while you control the amount and the timing, is a way to soften that later spike.

When your current bracket is genuinely low relative to your history. A layoff year, an early-retirement gap year, a year with unusually high deductions. Converting into a temporarily low bracket is one of the more defensible reasons to do it, since the discount is real and quantifiable.

When leaving tax-free assets to heirs matters to you. Since Roth IRAs aren't subject to lifetime RMDs for the original owner, the balance can continue growing tax-free for as long as you're alive. That's a separate consideration from your own retirement income needs, and it's worth naming explicitly rather than treating it as an automatic yes. It only strengthens the case if legacy planning is actually a goal for you.

When a conversion tends to backfire

When it pushes you across a Medicare IRMAA threshold. This is the one that catches people off guard often, because the penalty shows up two years later, not right away. Medicare bases your Part B and Part D premium surcharges on your modified adjusted gross income from two years prior. For 2026, the standard Part B premium is $202.90 a month. Once your MAGI crosses $109,000 as a single filer or $218,000 filing jointly, the premium jumps to $284.10 a month per person, an increase of $81.20 a month, or roughly $974 a year, and it keeps climbing in tiers from there⁽⁵⁾.

This means a Roth conversion large enough to cross that line doesn't just cost you income tax. It can cost you over $1,000 a year in higher Medicare premiums two years down the road, for both you and your spouse if you're both enrolled.

When you have other pretax IRA money and try to convert only the after-tax portion. If you've made non-deductible contributions to a traditional IRA and also hold pretax money in any traditional, SEP, or SIMPLE IRA, the IRS doesn't let you cherry-pick which dollars you convert. The pro-rata rule treats all your traditional IRA balances, across every account and every custodian, as one combined pool, and taxes your conversion proportionally based on the pretax-to-after-tax ratio of that whole pool⁽⁶⁾.

Someone with $90,000 in pretax IRA money and $10,000 in after-tax contributions who converts $10,000 will find that roughly 90% of it is still taxable, not the 0% they may have expected.

Tracking your after-tax basis with Form 8606 every year you make a non-deductible contribution is the only way to keep this calculation accurate⁽⁷⁾.

When you'd need to pay the tax bill out of the converted funds themselves. Paying the tax from the IRA reduces the amount that actually lands in the Roth account and starts growing tax-free, which weakens the entire premise of the strategy. If under 59 and a half, it can also trigger a 10% early withdrawal penalty on the withheld portion. The stronger approach is paying the tax bill from savings or a taxable account, so the full converted amount keeps working.

When you're still years away from retirement and expect your income to keep rising. If you're in your peak earning years and your bracket is already high, converting now often means paying tax at a rate that's higher, not lower, than what you're likely to face after you retire and your income drops. This is the mirror image of the low-income retirement window described above, and it's easy to overlook if you're focused on the general appeal of tax-free growth without running the actual comparison.

When you might need the money within five years. Each conversion has its own five-year clock. If you're under 59 and a half and withdraw converted principal before that conversion's five years are up, you can owe a 10% penalty on the amount withdrawn, on top of the income tax you already paid at conversion. Earnings on converted funds are subject to a separate five-year rule tied to when the Roth IRA was first opened, for tax-free withdrawal treatment⁽⁸⁾. A conversion isn't the right tool for money you might need to touch in the near term.

Why the decision is permanent

Before 2018, if a conversion turned out to be a mistake, perhaps the market dropped right after you converted, or your income situation changed, you could recharacterize it and undo the whole thing. That option is gone. Since the Tax Cuts and Jobs Act took effect, a conversion from a traditional IRA to a Roth IRA can no longer be recharacterized, for any reason⁽⁴⁾. Once you convert, the income is reported, the tax is owed, and there's no undo button.

That permanence is exactly why the bracket-filling approach, converting a deliberate, calculated amount rather than a round number, tends to be the more defensible strategy. It's harder to regret an amount you chose because it filled available room in a known tax bracket than an amount you chose because it felt like a good round figure.

Here are some common mistakes people make with Roth conversions:

• Converting a large lump sum without checking the IRMAA thresholds. People run the income tax math carefully and completely skip the Medicare premium math, then get a surprise letter from Social Security two years later.
• Assuming a conversion is either fully tax-free or fully taxable. If you've never tracked your IRA basis on Form 8606, or you're not sure whether you have pretax money sitting in an old rollover IRA somewhere, the pro-rata rule may apply in ways you haven't accounted for. It's worth pulling your Form 8606 history before converting anything.
• Treating "convert everything now" as the safe choice. Some people convert their entire balance in one year to be done with it. That approach can push a huge amount of income into the highest brackets you'll ever see, when spreading the same conversion across several years at a lower bracket each time would have cost meaningfully less in total tax.
• Forgetting that the decision is permanent before hitting confirm. Because recharacterization is no longer available for conversions made in 2018 or later, there's no safety net if the amount turns out to be larger than intended⁽⁴⁾. Reviewing the exact dollar figure, and how it interacts with your other income for the year, before submitting the conversion is worth the extra few minutes.
• Not coordinating the conversion with Social Security timing. If you've already started Social Security benefits, a portion of those benefits may become taxable once your combined income rises, and a large conversion can push more of that benefit into taxable territory in the same year. Looking at the conversion and your Social Security claiming strategy together, rather than as two separate decisions, tends to produce a clearer picture of the total tax impact.

None of this replaces a conversation with someone who can see your full tax return, your account balances, and your timeline together. The right conversion amount for your specific bracket, your specific RMD schedule, and your specific Medicare timing is a calculation worth running with a professional rather than estimating on your own.

A financial advisor can help determine the path forward and talk through whether a Roth conversion fits your situation this year. You can get matched with an advisor by answering a few questions:

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About the Author

The Greensprout Editorial Team covers retirement, tax, and personal finance topics for adults planning the next phase of their financial lives. Content is researched using primary sources, including the IRS, CMS, and major financial institutions.

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