Roth Conversion the Year You Retire

The year you retire is usually your lowest-income year since early in your career. Earned income stops on a specific date — not gradually, but cleanly. That creates a bracket room calculation that is often larger than any subsequent year will offer, because future years layer in Social Security income, pension distributions, or both. For many retirees, this is the single best Roth conversion opportunity of the entire golden window.

But the retirement year also has complications that no other year has: partial earned income that you have to estimate before it finalizes, a conversion deadline that falls on December 31 while your income isn't confirmed until your last paycheck clears, and two separate constraints — ACA or IRMAA — that depend entirely on whether you retire before or after 65.

This guide walks through the retirement-year mechanics specifically: how to calculate your bracket room, when in the year to act, and how the two most common constraints shape the decision.

Why the retirement year is different

In every prior working year, your income fills most or all of the lower tax brackets — 10%, 12%, 22% — leaving little room for a tax-efficient conversion without spillover into 24% or higher. In retirement years that follow, Social Security and RMDs gradually rebuild your income and compress that room again.

The retirement year sits between those two states. Depending on your retirement date, your earned income might represent only 25–75% of a full year's pay. That gap — the bracket room between your partial earned income and the next tier threshold — is the conversion window.

The formula is straightforward:

One constraint almost always bites before you hit the 22% ceiling. Which one depends on your age at retirement.

The Q4 timing advantage

You don't have to size the conversion in January. Unlike IRA contributions, Roth conversions must be completed by December 31 — but that means you have all year to plan and the entire fourth quarter to execute with precision.

The practical approach for most retirees:

• October–November: Confirm your final paycheck has cleared. Calculate total earned income YTD. Add any other income — pension payments, dividends, interest. Now you know your actual income baseline.
• November–December: Calculate bracket room and apply your constraint ceiling (ACA or IRMAA). Initiate the conversion. Arrange tax payment from outside funds or adjust quarterly estimates.
• December 31: Hard cutoff. Conversion must complete — funds must leave your traditional IRA and arrive in the Roth IRA — by this date.²

Waiting until Q4 reduces the risk of under- or over-converting. If you convert in February and then receive an unexpected bonus or your spouse takes a freelance project, you can't undo it — recharacterization was permanently eliminated by TCJA 2017.³

If you retire before 65: the ACA constraint

From the year you retire until you enroll in Medicare at 65, health insurance typically comes from the ACA Marketplace. This creates a hard income ceiling for Roth conversions: the 400% Federal Poverty Level cliff.

In 2026, crossing $62,600 MAGI (single) or $84,600 MAGI (couple) eliminates your advance premium tax credit entirely — a $10,000–$25,000 annual loss, depending on plan and location.⁴ Roth conversions count as ordinary income for MAGI purposes, so any conversion that pushes you above the cliff costs you the full credit for the year.

The ACA cliff is almost always more binding than the tax bracket ceiling for pre-65 retirees with partial earned income. A couple who earns $65,000 through June retirement has $84,600 − $65,000 = $19,600 of conversion room under the ACA cliff. The 22% bracket ceiling ($211,400 MFJ taxable income) would allow much more — but the ACA cliff governs.

If your earned income alone already exceeds the ACA cliff — as with a late-year retirement — you've lost the credit regardless of any conversion. At that point the constraint shifts: you can now convert up to the 22% or 24% bracket ceiling (or MAGI $218K for a future IRMAA cap) without a marginal ACA cost, because you're already above the cliff.

Pre-65 worked example — Michael and Linda, retiring mid-year

Michael and Linda are both 63. Michael retires April 30, 2026. Linda retired last year.

• Michael's earned income, January–April: $62,000
• Linda's income: $0 (no pension, no SS yet)
• IRA balance: $1.7M (Michael's; Linda has separate $400K)
• ACA Marketplace coverage, family plan, $1,800/mo premium with credit

Total 2026 MAGI without conversion: $62,000
ACA cliff: $84,600 (couple)
Maximum IRMAA-safe conversion: $84,600 − $62,000 = $22,600

At $22,600 converted: MAGI = $84,600 (right at cliff). They keep their premium credit. Federal tax on conversion at 22% = ~$4,972. They pay from outside funds (taxable savings), not from the IRA.

This is not a large conversion — but it is the right one for the year. Starting in 2027, no earned income at all means ACA-phase conversions at full $84,600 ceiling. At 65, Medicare enrollment removes the ACA constraint and IRMAA Tier 1 at $218,000 MAGI becomes the new ceiling.

If you retire at 65 or later: the IRMAA constraint

For retirees who enter retirement already on Medicare, the ACA cliff doesn't apply. The dominant conversion constraint is the IRMAA Tier 1 threshold: $109,000 MAGI (single) / $218,000 MAGI (MFJ).⁵

IRMAA uses a two-year lookback — your 2026 income determines your 2028 Medicare Part B premiums. The year you retire may be the last year you have substantial earned income, making it the last year IRMAA lookback creates a meaningful conversion ceiling. After this, lower post-retirement income opens the IRMAA window further.

Post-65 worked example — Robert and Carol, retiring late in the year

Robert, 67, retires September 30, 2026. Carol, 65, retired last year.

• Robert's earned income, January–September: $135,000
• Carol's income: $28,000 pension (started 2025)
• Combined other income: $163,000
• IRA balance: $2.3M (combined)
• Both on Medicare Part B

IRMAA Tier 1 threshold (MFJ): $218,000
Maximum conversion without crossing Tier 1: $218,000 − $163,000 = $55,000

At $55,000 conversion: MAGI = $218,000 (right at the Tier 1 line). Keeps base Medicare Part B premium at $202.90/person/month. Tax on conversion: largely at 22% with partial 24% spillover.

Note the bracket math: taxable income = $163,000 − $32,200 (std deduction) = $130,800. The 22% bracket ceiling for MFJ is $211,400 taxable income. Room = $211,400 − $130,800 = $80,600. But IRMAA caps the conversion at $55,000 ($218K MAGI). IRMAA, not the bracket, is binding.

Starting in 2027 with zero earned income and only Carol's $28,000 pension, the IRMAA window widens dramatically: MAGI ceiling rises to $218,000 − $28,000 = $190,000 of conversion room per year before Tier 1. Robert's late-year retirement meant a smaller conversion in year one, followed by much larger ones immediately after.

The IRMAA lookback starts now, even if you're not yet on Medicare

If you retire at 62, 63, or 64, you won't start Medicare for two or three years. But your retirement-year income is already entering the IRMAA lookback window. Your 2026 income determines your 2028 Medicare premiums. If you retire in 2026 at 63, your Medicare starts at 65 in 2028 — and the income you report on your 2026 tax return sets your initial Part B premium tier.

A retirement-year conversion that pushes your MAGI above $109,000 (single) or $218,000 (couple) in 2026 will cost you an extra $81.20 per person per month starting the moment you enroll in Medicare in 2028. That's a two-year delayed cost you're paying right now.

This isn't necessarily a reason to avoid the conversion — paying $1,950/person extra per year for two years may still be worth converting at 22% rather than 32% later. But it needs to be in the calculation.

Rolling your 401(k) this year

Many retirees roll their former employer 401(k) to a traditional IRA in the same year they retire. This timing matters for two reasons.

Pro-rata rule: Once your 401(k) balance lands in an IRA, it becomes part of your total IRA pool for pro-rata calculations. If you have existing non-deductible IRA basis, a large 401(k) rollover can dilute that basis and increase the taxable portion of any conversion. If pro-rata is a concern, consider the 401(k)-to-Roth direct rollover instead, or roll the 401(k) to a new IRA after any planned partial Roth conversions are complete.⁶

The rollover itself is not a taxable event — only the conversion is. A $600,000 direct trustee-to-trustee rollover from a 401(k) to a traditional IRA does not increase your taxable income for the year. It simply moves the balance into the IRA pool, from which you then decide how much to convert.

What to do in October–December of your retirement year

1. Confirm your total year-to-date income. Pull your most recent pay stub or final paycheck. Add any pension payments, interest, dividends, and capital gain distributions received through year-end.
2. Identify your binding constraint. Under 65: ACA cliff (single $62,600 / couple $84,600). Age 65+: IRMAA Tier 1 ($109K single / $218K MFJ). Choose the one that limits you more.
3. Calculate your conversion amount. Constraint ceiling minus total other income. Sanity-check against your 22% bracket ceiling (taxable income, not MAGI).
4. Contact your IRA custodian to initiate conversion. Direct same-custodian conversion is the simplest path — no withholding, immediate Roth credit. Allow a few business days before December 31.
5. Arrange tax payment from outside funds. Do not withhold from the conversion itself — that amount never reaches the Roth IRA and permanently loses compounding potential. Use taxable savings or a December estimated tax payment (IRS Form 1040-ES, Q4 due January 15).²
6. Track Form 8606. Every conversion creates basis tracking. File Form 8606 with your return to document the conversion — even if fully taxable. A $50 penalty applies for failure to file.⁷

The bigger picture: year one is just the start

The retirement year sets your conversion baseline. It's often the year with the most precision because your income is the most predictable — one job, one retirement date, no RMD variable yet. But it's not the only year. The golden window typically runs 10–15 years, and the optimal annual amount shifts each year as Social Security starts, as RMD age approaches, as market values change, and as bracket thresholds inflate.

A year-one conversion of $20,000–$60,000 might look modest. Over a 10-year plan with an advisor coordinating bracket fills, IRMAA management, Social Security timing, and estate planning, the total conversion could be $500,000–$1,200,000 — and the lifetime tax savings can reach $200,000–$500,000 on a $2M IRA.

Sources

1. IRS Rev. Proc. 2025-32 — 2026 standard deductions ($32,200 MFJ / $16,100 single) and tax brackets. irs.gov/pub/irs-drop/rp-25-32.pdf
2. IRS Publication 590-A — Roth conversion deadline (December 31 of tax year) and estimated tax payment rules. irs.gov/publications/p590a
3. IRS — Recharacterization of Roth IRA conversions. Recharacterization of Roth conversions was permanently eliminated by the Tax Cuts and Jobs Act of 2017, effective for tax year 2018 and later. irs.gov — IRA FAQs: Recharacterization
4. HHS — 2026 Federal Poverty Level guidelines. ACA Marketplace 400% FPL cliff: $62,600 (1 person) / $84,600 (2 people). healthcare.gov
5. CMS / Kiplinger — 2026 IRMAA Medicare Part B surcharges. Tier 1 threshold: $109,000 MAGI (single) / $218,000 MAGI (MFJ). Base Part B premium: $202.90/month. kiplinger.com — Medicare Premiums 2026
6. IRS Notice 2014-54 — Tax treatment of split rollovers from qualified plans. Explains direct rollover mechanics and pro-rata implications for IRA conversions. irs.gov/pub/irs-drop/n-14-54.pdf
7. IRS Form 8606 instructions — §6693(b) $50 penalty for failure to file Form 8606 when required. irs.gov/forms-pubs/about-form-8606

2026 brackets and thresholds verified against IRS Rev. Proc. 2025-32 and CMS 2026 IRMAA fact sheet. ACA cliff based on 2025 HHS Federal Poverty Level guidelines (2026 guidelines expected to adjust slightly upward; verify at healthcare.gov before planning). Values verified June 2026.