Quick Answer: A multi-year Roth conversion plan works by converting a measured slice of a traditional IRA or 401(k) to a Roth account every year during a specific low-income window — typically the years after leaving work but before Social Security and required minimum distributions (RMDs) begin — rather than converting everything at once or doing nothing at all. For a retired couple filing jointly in 2026, that usually means converting enough each year to fill up to the top of the 12% or 22% federal bracket (roughly $100,800 or $211,400 of taxable income), while watching two quieter tripwires: the Medicare IRMAA surcharge, which uses your income from two years earlier, and the pro-rata rule, which can force after-tax IRA dollars to ride along with every conversion if you hold both pre-tax and after-tax money in traditional IRAs.
Who This Guide Is For: Retirees Living in the Income Gap Years
This guide is written for a specific kind of household: people who have stopped full-time work but have not yet turned on the income spigots that will define the rest of their retirement. Maybe you retired at 60 or 62 with a paid-off house and a seven-figure 401(k), and you are not planning to claim Social Security until 67 or later. Maybe you took a package at 58 and are bridging to Medicare with a subsidized marketplace plan. Maybe you sold a business and are living off cash and a taxable brokerage account while your IRA sits untouched. In every one of these cases, there is a window — sometimes three years, sometimes twelve — where your taxable income is unusually low relative to your net worth. That gap is the single best opportunity most retirees will ever get to move money from a tax-deferred account into a Roth account cheaply.
The mechanics of a Roth conversion are simple in isolation: you tell your custodian to move some or all of a traditional IRA or 401(k) balance into a Roth IRA, you report the converted amount as ordinary income on that year’s tax return, and the money then grows and can eventually be withdrawn tax-free, with no RMDs ever required from the Roth IRA itself. What makes this a planning problem rather than a one-time transaction is that the tax bill scales with how much you convert in a single year, and federal brackets are progressive. Convert too little and you leave cheap tax-bracket space unused every year the window is open. Convert too much in one year and you push dollars that could have been taxed at 12% or 22% into the 24%, 32%, or even 35% bracket instead. A multi-year plan exists to solve exactly that trade-off: spread the conversion across as many low-bracket years as the gap allows, refilling the same bracket ceiling annually instead of taking one large bite.
Why does this matter more now than it did a decade ago? Two structural facts changed the math. First, the 2017 tax law’s lower brackets were made permanent by the One Big Beautiful Bill Act signed in July 2025, removing the “these rates expire in 2026” deadline that used to push people toward rushed, oversized conversions before an assumed rate hike. Second, SECURE 2.0 pushed the RMD start age to 73 (rising to 75 for people born in 1960 or later), which means many retirees now have a longer gap between leaving work and being forced to draw down pre-tax accounts — and a longer runway over which a multi-year conversion plan can operate without the clock working against them.
The Core Mechanic: Filling a Bracket, Not Chasing a Number
The single habit that separates a disciplined multi-year plan from an ad hoc one is bracket-filling arithmetic done every single year, not a flat dollar target picked once and repeated on autopilot. Because your other income, the standard deduction, and the bracket thresholds all move slightly year to year, the conversion room available to you changes too. The formula is the same every time:
Conversion room this year =
Target taxable-income ceiling − other taxable income + standard deduction
For 2026, a married couple filing jointly takes a standard deduction of roughly $32,200 (a single filer’s is about $16,100). The federal brackets that matter most for retirees sitting on large IRAs are the 12% bracket, which runs up to about $100,800 of taxable income for joint filers, and the 22% bracket, which runs up to roughly $211,400. Above that, the 24% bracket extends to about $403,550. Single filers see roughly half those thresholds: about $50,400 for the top of 12%, and about $105,700 for the top of 22%.
Once you know your target ceiling, everything else is arithmetic. If a couple has $12,000 of interest and dividend income and wants to fill exactly to the top of the 22% bracket, they can convert $211,400 + $32,200 − $12,000 = $231,600 that year without any of the converted dollars being taxed above 22%. Do that calculation fresh every January using that year’s actual other income, and the plan self-corrects instead of drifting.
Why the Withdrawal Order Around the Conversion Matters
A conversion itself does not require you to touch your Roth or spend anything — it is a transfer between account types, not a distribution to your checking account. But you still have to pay the resulting tax bill from somewhere, and where that cash comes from changes the value of the whole strategy. Paying the conversion tax out of taxable savings, rather than withholding it from the IRA itself, means every converted dollar keeps compounding tax-free inside the Roth. Withhold the tax from the conversion and you shrink the amount that actually reaches the Roth, which quietly reduces the benefit of the whole maneuver. Most fee-only planners treat “pay the tax from outside money” as close to a hard rule for anyone doing a multi-year plan, because the difference compounds for decades.
The Five-Year Clock, the Pro-Rata Rule, and Other Mechanics That Bite Multi-Year Planners Specifically
Two rules matter far more to someone converting repeatedly over several years than to someone doing a single one-off conversion, because repetition multiplies their effect.
Each Conversion Starts Its Own Five-Year Clock
Converted principal can always be withdrawn tax-free once it has been in a Roth account, because you already paid tax on it. But if you are under 59½ and want to touch converted funds early, each year’s conversion has its own five-year holding period before that specific batch of converted principal is free of the 10% early-withdrawal penalty. A retiree running a five-year conversion plan is technically opening five separate five-year clocks, one per conversion year. In practice this rarely causes real damage, since the ordering rules let you withdraw converted amounts oldest-first and most gap-year retirees are not touching Roth principal early anyway — but it is worth tracking if a health emergency or unplanned expense means you need access sooner than the calendar assumed.
The Pro-Rata Rule Punishes People Who Forget What Else Is in Their IRAs
If you have ever made a nondeductible (after-tax) contribution to a traditional IRA, or rolled over a 401(k) that contained after-tax dollars, you have basis sitting inside your IRA that the IRS tracks on Form 8606. The pro-rata rule says you cannot cherry-pick that after-tax basis to convert tax-free while leaving the pre-tax money behind. Every conversion is treated as pulling a proportional slice of pre-tax and after-tax money across all of your traditional, SEP, and SIMPLE IRAs combined, valued as of December 31 of the conversion year. Someone running a multi-year plan needs to recompute this ratio every year, because rolling new money into a traditional IRA, taking a distribution, or making another nondeductible contribution all change the blend. Forgetting this is one of the most common multi-year-specific mistakes, covered in more detail below.
Conversions Are Permanent — There Is No Recharacterization Safety Net Anymore
Before 2018, if a conversion turned out to be a bad idea — the market dropped right after you converted, say — you could undo it through recharacterization. That escape hatch closed with the 2017 tax law and has not returned. Every conversion in a multi-year plan is a one-way door: once it settles, that year’s tax bill is locked in regardless of what the account does afterward. This is exactly why sizing each year’s conversion carefully, rather than converting a round number out of habit, matters more in a repeated multi-year plan than in a single transaction you might be more careful about.
Where IRMAA and the Net Investment Income Tax Quietly Change the Math
Federal income tax brackets are the visible cost of a conversion. Two other costs are easy to miss because they show up later and are calculated on a different measure of income than the one most people watch.
Medicare’s income-related monthly adjustment amount, or IRMAA, raises Part B and Part D premiums for higher earners, and it is based on modified adjusted gross income (MAGI) from your tax return filed two years earlier. A large conversion in 2026 will not touch your Medicare premium in 2026 or even 2027 — it shows up on your 2028 Medicare bill. For 2026, the first IRMAA tier applies once MAGI for the 2024 tax year exceeded roughly $106,000 for a single filer or $212,000 for a married couple filing jointly, with additional tiers stepping up from there. Because IRMAA is a step function rather than a smooth curve, crossing a threshold by even a few hundred dollars can add well over a thousand dollars a year in combined Part B and Part D surcharges for a couple, for the full year the tier applies. A multi-year planner who is only 66 or older and on Medicare needs to treat these thresholds as additional bracket lines on top of the ordinary tax brackets, and often deliberately converts just under an IRMAA tier rather than up to the nearest round tax bracket.
The 3.8% net investment income tax (NIIT) works differently: the conversion itself is not investment income and is never directly subject to NIIT. But because NIIT applies once MAGI crosses $200,000 (single) or $250,000 (married filing jointly), a large conversion that pushes MAGI over those thresholds can pull your other investment income — interest, dividends, capital gains sitting in a taxable brokerage account — into NIIT for that year, even though the converted dollars themselves escape the tax. This interaction is one reason a moderate, repeated conversion often beats one large one: it is easier to stay under NIIT and IRMAA thresholds every year than to clear them once and then spend a year cleaning up the side effects.
A Worked Example: The Alvarez Household’s Five-Year Window
Consider a hypothetical couple, both age 62 in 2026, who just retired with a combined $1.4 million across traditional IRAs and old 401(k) balances now rolled into IRAs. They have no pension. Their taxable brokerage account throws off about $10,000 a year in interest and qualified dividends. They plan to claim Social Security at 67, in 2031, and will not face RMDs until 73, in 2037. That leaves a genuine five-year runway, 2026 through 2030, where their only income is that $10,000 of investment income plus whatever they choose to convert.
Using the 2026 joint-filer numbers — a $32,200 standard deduction, a 12% bracket ceiling near $100,800 of taxable income, and a 22% bracket ceiling near $211,400 — three plausible annual conversion targets emerge, shown in the comparison table and bar chart below. Each strategy fills a different bracket ceiling every year for as long as the $1.4 million balance lasts.
Years Needed to Convert a $1.4 Million IRA, by Strategy
Illustrative example based on a $1.4M combined traditional IRA balance, 2026 joint-filer brackets and standard deduction, and $10,000 of other annual income. Bar widths scaled to years needed; excludes growth on the remaining balance during the conversion period.
The conservative path never leaves the 12% bracket and takes over a decade to fully convert the balance — well beyond their five-year gap, meaning they would still be converting after Social Security starts, at which point the math has to be redone with that new income layered in. The moderate path finishes almost exactly within their five-year window, converting about $233,600 a year and paying a top marginal rate of 22% on the last dollar converted each year. The aggressive path finishes in about 3.3 years but pushes into the 24% bracket every year it runs, and at roughly $233,600–$425,750 of MAGI, it would also trip the first IRMAA tier for whichever spouse is within two years of Medicare eligibility, and would pull their brokerage account’s dividends and interest into NIIT territory as well.
The moderate strategy is the one most fee-only planners would recommend for a household in this exact position: it uses the entire five-year gap, never pays more than 22% on a converted dollar, and stays under both the NIIT and the first IRMAA threshold in every year of the plan. It also leaves nothing to convert once Social Security begins, so the couple does not have to re-run the analysis under a higher-income backdrop.
Reference Table: Matching a Conversion Strategy to Your Situation
| Strategy | 2026 Taxable Income Ceiling (MFJ) | Top Marginal Rate Paid | IRMAA Risk (2 Years Later) | Best Suited For |
|---|---|---|---|---|
| Conservative — fill to 12% | ~$100,800 | 12% | Very low | Long gap years (8+ years to RMD age), other income already low, priority on minimizing lifetime tax paid over speed |
| Moderate — fill to 22% | ~$211,400 | 22% | Low, but check the year Medicare starts | Typical 4–7 year gap, moderate-to-large IRA balance, goal of finishing the conversion before Social Security or RMDs begin |
| Aggressive — fill to 24% | ~$403,550 | 24% | High — likely triggers first or second tier | Short gap (2–3 years), very large IRA relative to income, strong conviction that future rates or RMDs will be materially worse |
Notice the dashed line most planners implicitly draw at the 22%/24% boundary: staying at or below 22% keeps the plan inside a bracket that has held steady for years, while crossing into 24% and beyond starts stacking IRMAA and NIIT exposure on top of the higher marginal rate itself. That boundary is worth marking mentally the same way you would mark a hard budget limit — it is the point past which “converting a little more this year” starts costing meaningfully more than the tax table alone suggests.
Common Mistakes in Multi-Year Roth Conversion Plans
A single conversion is hard to get wrong in a way that compounds. A multi-year plan gives small errors five, seven, or ten chances to repeat, which is why the mistake list below skews toward habits rather than one-off miscalculations.
- Converting the same dollar amount every year without recalculating. Bracket thresholds, your standard deduction, and your other income all shift annually. A number that filled the 22% bracket perfectly in year one can spill into 24% by year three if other income rises or thresholds move less than expected.
- Forgetting the pro-rata rule after a 401(k) rollover. Rolling an old 401(k) with after-tax contributions into a traditional IRA mid-plan changes the pre-tax/after-tax blend for every conversion that follows, including ones already scheduled for later in the same year.
- Withholding the conversion tax from the IRA itself. This shrinks the amount that actually lands in the Roth and, if you are under 59½, the withheld portion can also be hit with the 10% early-withdrawal penalty since it never reaches the Roth as a conversion.
- Ignoring the two-year IRMAA lookback. Treating a conversion year and the Medicare premium year as if they were the same year leads people to convert aggressively at 64 without realizing the surcharge lands right as Medicare coverage starts at 65.
- Not coordinating with state income tax. A handful of states tax Roth conversions the same as ordinary income with no special treatment, and a couple of states offer partial retirement-income exclusions that a large conversion can burn through in a single year, reducing the exclusion’s value for other retirement income received the same year.
- Treating the plan as irreversible-proof against market timing. Because recharacterization no longer exists, converting a large lump sum right before a market downturn locks in tax on a value the account may not hold for months or years. Smaller, repeated conversions dampen this timing risk simply by spreading it out.
- Overlooking capital gains stacking. Ordinary income from a conversion sits at the bottom of the stack and can push otherwise 0%-taxed long-term capital gains in a taxable brokerage account into the 15% bracket, an effect that is easy to miss if you only look at the ordinary-income bracket table.
A Practical Checklist for Running the Plan Year by Year
- Project the household’s income for the current calendar year before converting anything — interest, dividends, part-time consulting, pension income, anything taxable.
- Recalculate the conversion room using this year’s actual standard deduction and bracket thresholds, not last year’s numbers.
- Check the calendar for Medicare enrollment: if either spouse turns 65 within the next two years, model the IRMAA impact of this year’s conversion before finalizing the amount.
- Pull Form 8606 for every household member with a traditional IRA and confirm the current pre-tax/after-tax basis ratio before applying the pro-rata rule.
- Decide in advance where the tax payment will come from — ideally taxable savings, not IRA withholding — and set aside that cash before initiating the transfer.
- Time the conversion request with enough of the calendar year left to correct course if a major unexpected income event shows up later in the year.
- Confirm with your custodian that the transfer is coded as a Roth conversion, not a distribution followed by a separate contribution, to avoid contribution-limit and 60-day rollover complications.
- File Form 8606 for the conversion and update your basis tracking for next year’s calculation.
- Revisit the plan’s total remaining balance and years-to-completion estimate at year-end, adjusting next year’s target if the account’s growth or a spending change has shifted the picture.
Households already comfortable with the basics of Roth accounts sometimes underestimate how many of these mistakes stem from treating a Roth IRA like a static savings vehicle rather than a moving tax strategy; a good general primer on the most common Roth IRA mistakes and how to avoid them is worth reviewing alongside this multi-year framework, since several of the same account-level errors — missed basis tracking, five-year-rule confusion, and contribution mix-ups — resurface inside a conversion plan too.
Key Takeaways
- A multi-year Roth conversion plan spreads conversions across the low-income years between leaving full-time work and the start of Social Security and RMDs, refilling a chosen bracket ceiling every year instead of converting once.
- The core formula never changes: conversion room equals your target taxable-income ceiling, plus your standard deduction, minus your other taxable income for that specific year.
- For most 2026 joint filers with a substantial IRA and a multi-year gap, filling to the top of the 22% bracket (about $211,400 of taxable income) balances speed against cost better than either the ultra-conservative 12% approach or an aggressive push into 24% and above.
- IRMAA is assessed on a two-year lookback and the pro-rata rule applies across all of your traditional IRAs combined, so both need to be rechecked every single year of a multi-year plan, not just once at the start.
- Conversions cannot be undone through recharacterization, so sizing each year’s amount deliberately — rather than repeating a round number — matters more the more years the plan runs.
Frequently Asked Questions
How many years should a multi-year Roth conversion plan run?
Most plans run for the length of the actual income gap — the years between when you stop earning a full paycheck and when Social Security, a pension, or required minimum distributions push your income back up. That can be as short as two or three years or as long as a decade, depending on when you retire and when you claim benefits. There is no fixed ideal length; the plan should run exactly as long as your low-income window lasts.
Does converting a large amount in one year always cost more than spreading it out?
Usually, yes, if your income would otherwise stay low across multiple years. Because federal brackets are progressive, cramming ten years’ worth of conversions into two years pushes a large share of the money into higher brackets that a spread-out plan would have avoided entirely. The exception is a household that expects a large permanent increase in income or tax rates very soon, where converting faster at a slightly higher rate now can still beat waiting.
What is the pro-rata rule and why does it matter for repeated conversions?
The pro-rata rule requires every Roth conversion to include a proportional mix of pre-tax and after-tax dollars from all your traditional, SEP, and SIMPLE IRAs combined, rather than letting you convert only the after-tax portion tax-free. It matters especially for multi-year plans because rollovers, new contributions, or distributions in any year can change that ratio, so it needs to be recalculated before each year’s conversion, not assumed to stay constant.
How does IRMAA interact with a multi-year conversion plan?
Medicare’s income-related premium surcharge, IRMAA, is based on your tax return from two years earlier. A conversion done at age 63 will not affect your premiums until age 65, when Medicare coverage and the associated premium calculation begin. Anyone within two years of Medicare eligibility should model the IRMAA impact of each year’s conversion before finalizing the amount, since crossing a threshold triggers the full surcharge for that income tier, not a partial one.
Can I change my mind after converting if the market drops?
No. Recharacterization, which used to let you undo a conversion, was eliminated for tax years starting in 2018 and has not been reinstated. Once a conversion settles, the tax on that amount is owed regardless of what happens to the account’s value afterward. This is one reason multi-year plans that convert smaller amounts repeatedly tend to carry less regret risk than a single large conversion executed at one point in time.
Should I pay the conversion tax from the IRA or from other savings?
Paying from other savings, such as a taxable brokerage or checking account, is almost always better. Withholding the tax from the IRA reduces the amount that actually reaches the Roth account, shrinking the tax-free growth you are trying to capture, and if you are under 59½ the withheld amount can also trigger the 10% early-withdrawal penalty since it is treated as a distribution rather than part of the conversion.
References
- Internal Revenue Service — Retirement Topics: Rollovers of Retirement Plan and IRA Distributions
- Internal Revenue Service — Form 8606 Instructions (Nondeductible IRAs)
- Internal Revenue Service — Revenue Procedure setting 2026 inflation-adjusted tax brackets and standard deduction amounts
- Centers for Medicare & Medicaid Services — Medicare Part B and Part D Income-Related Monthly Adjustment Amount (IRMAA) tables
- Social Security Administration — Retirement Benefits: Full Retirement Age and Delayed Claiming Credits
- Congressional research summaries on SECURE 2.0 Act required minimum distribution age changes
