Roth Conversion Timing in Retirement

Strategic Roth conversions are one of the highest-leverage tax moves available in retirement planning — and most people botch the timing. The pattern is predictable: you retire, your income drops, a multi-year window of low tax brackets opens up, and you either ignore it entirely or panic-convert everything in one year (triggering Medicare surcharges and an unnecessary tax spike). The practitioner's approach is different. It's bracket-filling conversions spread across the gap years between retirement and RMDs — sized precisely to exploit today's historically favorable rates while dodging the IRMAA cliffs that eat into your savings.

Why the Pre-RMD Window Is Your Highest-Value Conversion Opportunity

The years between retirement and age 73 (when required minimum distributions kick in) create a tax valley that most retirees don't recognize until it's gone. Here's the income trajectory that makes this window so valuable:

Working years (40-62): Your salary fills brackets up to 22-32%. No room for conversions without paying top marginal rates.

Early retirement (60-72): Salary disappears. Social Security may not have started yet. Your taxable income might be near zero — the lowest brackets you'll ever see.

RMD years (73+): Forced distributions from traditional accounts layer on top of Social Security, pensions, and investment income. You're back in higher brackets with zero flexibility.

The signal worth remembering: you get roughly 10-12 years of low-bracket opportunity, and every year you waste is conversion space you'll never recover. Once RMDs begin, your traditional IRA is on autopilot — the IRS decides how much comes out, not you.

2025 Tax Brackets (The Numbers That Drive Your Conversion Math)

Your conversion sizing starts with knowing exactly where the bracket boundaries sit. For 2025:

The standard deduction for 2025 is $15,750 (single) or $31,500 (married filing jointly). If you're 65 or older, you get an additional standard deduction — and under the One Big Beautiful Bill Act, seniors can claim an extra $4,000 deduction (for 2025 through 2028), though it phases out above $75,000 MAGI for single filers and $150,000 for joint filers.

The point is: your first $31,500 of income as a married couple is tax-free, and your next $96,950 is taxed at just 10-12%. That's enormous conversion headroom if your other income is modest.

The TCJA Story: Why These Rates Are Locked In (But Not Forever Cheap)

The One Big Beautiful Bill Act made the Tax Cuts and Jobs Act rates permanent — the feared 2026 "sunset" where brackets would revert to higher pre-2018 levels (12% jumping to 15%, 22% to 25%, 24% to 28%) no longer applies. That's the good news.

The nuance: while the rate structure is now permanent, the new senior deduction ($4,000) sunsets after 2028. And some of the OBBBA's temporary provisions — including enhanced standard deductions — will phase out in coming years. The planning implication is straightforward: the next few years remain an unusually favorable window for conversions, even though the original TCJA cliff has been eliminated.

Bracket-Filling (The Core Conversion Discipline)

Bracket-filling is exactly what it sounds like: you calculate how much room remains in your target tax bracket after accounting for all other income, then convert precisely that amount from traditional to Roth.

The formula: Conversion Amount = Top of Target Bracket − Current Taxable Income

Your situation: You and your spouse are 64, recently retired. Your 2025 income looks like this:

• Taxable Social Security: $0 (you're delaying until 67)
• Capital gains and dividends from taxable accounts: $12,000
• Part-time consulting: $0
• Gross income: $12,000
• Standard deduction (married, both 65+): −$31,500
• Taxable income before conversion: $0

You have $96,950 of space in the 12% bracket and another $109,750 in the 22% bracket (for a combined total of $206,700 to the top of the 22% bracket). Even converting $100,000 keeps you entirely within the 22% bracket — and your effective federal rate on that conversion would be roughly 10-11% after the standard deduction and lower bracket fill.

Why this matters: if you skip conversions and let that $100,000 stay in your traditional IRA until RMDs, you'll pay 22% or more on every dollar — plus it stacks on top of Social Security and other income, potentially pushing you into the 24% bracket.

Common Bracket-Filling Targets

Your target bracket depends on the size of your traditional balance and your time horizon:

• Fill the 12% bracket if you have modest traditional balances (under $500,000) and expect 22%+ rates later. This is the conservative approach — low risk, clear savings.
• Fill the 22% bracket if you have $500,000–$1.5 million in traditional accounts and expect RMDs to push you into 24%+ territory. This is the sweet spot for most retirees.
• Fill the 24% bracket if you have $1.5 million+ in traditional accounts, because your RMDs at 73 will be large enough to push well into higher brackets (and trigger significant IRMAA surcharges).

The practical test: project your age-73 RMD and stack it on top of expected Social Security and pension income. If the result lands you in a higher bracket than your conversion bracket, the conversion pays for itself.

IRMAA Cliffs (The Hidden Tax That Wrecks Careless Conversions)

Medicare's Income-Related Monthly Adjustment Amount adds surcharges to your Part B and Part D premiums when your modified adjusted gross income exceeds certain thresholds. The critical detail: IRMAA operates as a cliff, not a gradient. One dollar over a threshold triggers the full surcharge for the entire year.

Here are the 2025 IRMAA thresholds (based on your 2023 tax return):

The two-year look-back: A conversion you execute in 2025 affects your 2027 Medicare premiums. This lag means you need to plan at least two years ahead — and it means a large conversion today creates a "premium echo" you'll feel 24 months later.

The cost of one bad dollar: If you're a married couple and your MAGI lands at $212,001 instead of $212,000, you each pay an extra $74/month in Part B premiums. That's $74 × 2 × 12 = $1,776 per year — a meaningful tax on a single dollar of excess income.

The real play: size your conversions to stay below the next IRMAA cliff, or blow through it deliberately when the long-term math justifies the surcharge. The worst outcome is accidentally creeping $1,000 over a threshold — you get almost no additional conversion benefit but pay the full surcharge penalty.

When to Deliberately Exceed an IRMAA Threshold

Sometimes the math favors accepting the surcharge. If you're converting $150,000 at a 10% effective rate to avoid paying 22-24% later on that same money, the $1,776 annual IRMAA surcharge (first tier for a married couple) represents just 1.2% of the conversion amount. Compare that to the 12-14% tax savings on the conversion itself — the surcharge is a rounding error against the long-term benefit.

The decision rule: if the IRMAA cost is less than 2-3% of your conversion amount, and the bracket savings exceed 5%, accept the surcharge and convert.

Worked Example: Five-Year Conversion Plan for a Married Couple

Your situation: Mark and Lisa, both 63, just retired with:

• Combined traditional IRA/401(k): $1,400,000
• Social Security (planned at 67): $52,000/year combined
• Taxable brokerage account: $350,000
• Annual spending need: $85,000
• No pension

Before conversions (ages 63-66): Their only taxable income is approximately $14,000 in dividends and capital gains from the brokerage account. After the $31,500 standard deduction, their taxable income is $0.

Conversion strategy: Convert $80,000 per year for five years (ages 63-67), targeting the top of the 12% bracket with significant room to spare below the first IRMAA cliff.

Year 1 tax calculation:

• Gross income: $14,000 (investments) + $80,000 (conversion) = $94,000
• Standard deduction: −$31,500
• Taxable income: $62,500
• Federal tax: $23,850 × 10% + $38,650 × 12% = $2,385 + $4,638 = $7,023
• Effective rate on the $80,000 conversion: roughly 8.8%

Over five years, they convert $400,000 at an average effective rate of approximately 8.8%, paying roughly $35,100 in total federal tax on conversions.

The comparison scenario (no conversions): Their $1,400,000 grows to approximately $1,750,000 by age 73 (assuming modest 3% real growth). First-year RMD at 73: roughly $66,000. Combined with Social Security ($52,000, of which ~$44,200 is taxable), their taxable income after deduction hits approximately $78,700 — putting them solidly in the 22% bracket.

Without the conversions, they'd pay roughly 22% on the first $66,000 of RMDs that falls in the upper brackets. By converting $400,000 at 8.8%, they avoid paying 18-22% on that same money later — a tax savings of approximately $37,000-$53,000 over their lifetimes, before accounting for the Roth's tax-free growth.

What matters here: the gap between your effective conversion rate (8-12%) and your projected RMD rate (18-24%) is your profit margin on the conversion. The wider that gap, the more aggressively you should convert.

The Pro-Rata Rule (Why IRA Consolidation Matters Before You Convert)

If you have both pre-tax and after-tax (non-deductible) contributions in your traditional IRAs, the IRS won't let you cherry-pick which dollars to convert. The pro-rata rule treats all your traditional IRA balances as one pool and taxes your conversion proportionally.

Example: You have $200,000 in traditional IRAs — $180,000 is pre-tax and $20,000 is after-tax (non-deductible) contributions. If you convert $50,000, the IRS doesn't let you claim you converted only the after-tax portion. Instead, 90% of your conversion ($45,000) is taxable and 10% ($5,000) is tax-free, matching the ratio across your total IRA balance.

The workaround (if your employer plan allows it): roll your pre-tax IRA balance into your current 401(k) before converting. This isolates the after-tax money in your IRA, letting you convert it with minimal tax. Not every plan accepts incoming rollovers, but it's worth checking — the tax savings can be substantial.

The practical point: know your pre-tax vs. after-tax IRA breakdown before executing any conversion. File Form 8606 to track your basis, and consolidate accounts if the pro-rata math works against you.

The Five-Year Rule (And Why It Rarely Matters in Retirement)

Each Roth conversion starts its own five-year clock. If you withdraw converted funds before five years have passed and you're under age 59½, you'll owe a 10% early withdrawal penalty on the converted amount (though not additional income tax, since you already paid that).

Here's the nuance that matters: if you're over 59½ when you convert — which most retirees are — the five-year rule on conversions is essentially irrelevant. You can withdraw converted funds immediately without penalty. The five-year rule only bites younger converters or those who need the money back quickly.

The one exception worth noting: the five-year rule for Roth earnings (separate from the conversion rule) requires your Roth account to have been open for at least five years before you can withdraw earnings tax-free. If you've never had a Roth IRA, open one now with even a small contribution to start the clock — even if you don't plan to convert for several years.

When Conversions Don't Make Sense (The Honest Assessment)

Not every retiree benefits from Roth conversions. Skip or limit conversions if:

• Your projected RMD bracket matches your current bracket. If you're already in the 22% bracket and expect to stay there, conversions just prepay tax at the same rate — no savings, just accelerated cash outflow.
• You'd need to pay conversion taxes from retirement funds. Pulling $20,000 from your IRA to pay tax on a $100,000 conversion defeats the purpose (you're converting less and losing the tax-deferred growth on the $20,000).
• You're charitably inclined and plan to use Qualified Charitable Distributions. QCDs let you donate up to $105,000 per year directly from your IRA to charity, satisfying your RMD without creating taxable income. If your charitable giving covers most of your RMDs, there's less income to worry about.
• You plan to relocate to a no-income-tax state. Converting while you live in California (13.3% top rate) and then moving to Florida means you paid state tax unnecessarily. Time the move before the conversions.

The test: does the conversion create a clear rate arbitrage between what you pay now and what you'd pay later? If the spread is less than 3-4 percentage points, the benefit may not justify the complexity and cash outflow.

Roth Conversion Planning Checklist (Tiered)

Essential (do these before any conversion)

These four steps prevent the most common and costly mistakes:

• Calculate your current taxable income including all sources — Social Security (taxable portion), pensions, dividends, capital gains, rental income
• Identify your target bracket ceiling and compute available conversion room (bracket top minus current taxable income)
• Check your MAGI against IRMAA thresholds — remember the two-year look-back (2025 conversions affect 2027 premiums)
• Confirm you have non-retirement cash to pay the tax bill — never pay conversion tax from the IRA itself

High-Impact (for optimized multi-year plans)

For retirees who want to maximize the conversion window systematically:

• Project your RMD-year income — stack estimated RMDs, Social Security, and other income to see your future bracket
• Map out a multi-year conversion schedule — determine annual conversion amounts that fill your target bracket each year through age 72
• Review pro-rata exposure — check Form 8606 for any after-tax IRA basis and consider rolling pre-tax money into a 401(k) to isolate it
• Coordinate with state tax planning — if you're in a high-tax state and considering relocation, time conversions accordingly

Optional (situational but valuable)

For retirees with specific circumstances:

• Model the OBBBA senior deduction phase-out — if your MAGI is near $75,000 (single) or $150,000 (joint), conversions may accelerate the phase-out of the extra $4,000 deduction
• Evaluate Qualified Charitable Distribution strategy as an alternative to conversions for the charitably inclined
• Open a Roth IRA now (even with $100) if you've never had one, to start the five-year earnings clock

Next Step (Put This Into Practice)

Pull up your most recent tax return and calculate your conversion headroom for this year.

How to do it:

1. Add up your 2025 projected gross income — Social Security, pensions, investment income, any earned income
2. Subtract your standard deduction ($15,750 single / $31,500 married filing jointly, plus age-65 additions)
3. Find your current taxable income on the bracket table above
4. Subtract that number from the top of your target bracket — the result is your maximum conversion amount before crossing into the next bracket
5. Cross-check against the IRMAA thresholds to confirm you won't accidentally trigger a Medicare surcharge cliff

Interpretation:

• Headroom over $100,000: You have significant conversion opportunity — consider aggressive annual conversions
• Headroom of $30,000-$100,000: Solid conversion window — execute annually through your pre-RMD years
• Headroom under $30,000: Conversions may still help, but size them carefully against IRMAA cliffs and state taxes

Action: If your headroom exceeds $30,000 and you have non-retirement cash to cover the tax bill, schedule your first conversion before December 31 — there are no extensions for Roth conversions, and every year you delay is a year of low-bracket opportunity lost.