Complete Roth Conversion Strategy Guide
Roth conversions done well are often the single most valuable financial move of a retiree's life. Done poorly, they burn tax needlessly. The difference is multi-year planning against bracket boundaries, IRMAA thresholds, and legacy goals.
Why conversions work
A traditional IRA is like a partnership with the government: they own the taxes on all future growth + principal. Convert to Roth and you pay the government's share now — ending the partnership. The math wins when:
- Your current tax bracket is meaningfully lower than your future tax bracket (RMD era, or from bracket increases in law).
- You have years of growth ahead of the Roth balance (compounding tax-free beats compounding tax-deferred).
- You're leaving money to heirs (inherited Roth = 10 years of tax-free growth + tax-free distributions vs. inherited traditional with ordinary-income tax on distributions).
The 60-73 golden window
For most retirees, this is when the math tilts strongly toward conversion:
- Age 60-65: Retired or semi-retired. Earned income dropped. Social Security not yet claimed (if delayed to 70). Lowest bracket of your life since your 20s.
- Age 65-70: Medicare starts; IRMAA becomes a factor. SS may start at 67. Window narrows.
- Age 70-72: SS is on. Pre-RMD but narrowing window. Last chance before RMDs kick in at 73.
- Age 73+: RMDs add mandatory income. Still possible to convert but your bracket is usually higher. Math weakens.
Bracket filling precision
The goal isn't to convert your whole balance in one year — that pushes you into the 32%+ bracket, negating the benefit. It's to convert just enough annually to fill your current (low) bracket without crossing into the next.
2026 federal brackets (MFJ, per IRS Rev. Proc. 2025-32):1
- 10% bracket: $0 – $23,200
- 12% bracket: $23,201 – $94,300
- 22% bracket: $94,301 – $201,050
- 24% bracket: $201,051 – $383,900
- 32% bracket: $383,901 – $487,450
- 35% bracket: $487,451 – $768,600
- 37% bracket: $768,601+
For a couple with $60K of non-conversion income, converting $141K tops off the 22% bracket precisely ($201,050 − $60,000 = $141,050 of conversion headroom). Annual re-calibration matters — each year your other income shifts.
IRMAA — the hidden cliff
Medicare Part B + D premiums surcharge above income thresholds. Two-year lookback: 2026 premiums are based on your 2024 MAGI. 2026 tiers (single filer; MFJ thresholds are 2×):2
- Tier 1: $109,000+ MAGI → +$81.20/mo Part B + $14.50/mo Part D
- Tier 2: $137,000+ → +$202.90/mo Part B + $37.40/mo Part D
- Tier 3: $171,000+ → +$324.64/mo Part B + $60.30/mo Part D
- Tier 4: $205,000+ → +$446.38/mo Part B + $83.10/mo Part D
- Tier 5: $500,000+ → +$487.00/mo Part B + $91.00/mo Part D
Base Part B premium in 2026: $202.90/month. MFJ thresholds are 2× the single-filer thresholds, topping out at $750,000. A conversion that bumps you into a higher tier adds $1,100-6,900/yr of Medicare premiums per person — an unexpected effective tax increase. Specialists keep conversions just below threshold edges, and appeal via Form SSA-44 when a life-event MAGI change (retirement, loss of income) is otherwise misrepresenting current ability to pay.3
5-year rule
Each Roth conversion has its own 5-year clock before the converted amount can be withdrawn penalty-free (if you're under 59½).4 Separate from the 5-year rule on Roth IRA contributions (which applies to earnings). For retirees 59½+ already, the 5-year conversion clock doesn't apply to withdrawals of converted funds — only the first-contribution 5-year clock applies to earnings. Still affects inherited Roth dynamics.
Pro-rata rule
If you have multiple traditional IRAs including ones with after-tax basis (backdoor Roth contributions, non-deductible contributions), the pro-rata rule treats all IRAs as a single pool for conversion purposes.5 You can't cherry-pick "just the after-tax portion" to convert. Track basis on Form 8606 annually. For those with meaningful basis: consider rolling pre-tax IRA balance into a 401(k) (which accepts incoming rollovers) to isolate the after-tax remainder in IRA, then convert cleanly. SEP and SIMPLE IRAs count toward the pro-rata pool; inherited IRAs do NOT.
Common mistakes
- Big one-year conversion. Pushes you into a high bracket. Multi-year ladder is almost always better.
- Ignoring IRMAA. The surcharge adds 1-3% to the effective cost of conversion.
- Converting in a high-state-tax year before moving to no-state-tax state. Time conversions after moving to FL/TX/WA etc. for meaningful state-tax savings.
- Converting too little. Most retirees err conservative. If bracket differential supports it, fuller conversion accelerates the benefit.
- Not tracking basis. Form 8606 each year with non-deductible contributions or post-tax rollovers. Lost basis = double taxation at withdrawal.
A fee-only Roth conversion specialist builds your multi-year plan: exact annual ceiling, IRMAA management, SS coordination, and a year-by-year schedule that maximizes lifetime tax savings. Free match, no obligation.
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- Tax Foundation — 2026 Federal Tax Brackets (per IRS Rev. Proc. 2025-32).
- Kiplinger — 2026 Medicare IRMAA Brackets. Base Part B: $202.90/month.
- SSA Form SSA-44 — IRMAA Life-Changing Event Appeal.
- IRC § 408A(d)(2) and (3) — Roth IRA Distribution Ordering Rules and 5-Year Rules.
- IRS Form 8606 — Nondeductible IRAs. Pro-rata rule under IRC § 408(d)(2).
- IRS — IRA Contribution Limits (2026 Roth contribution limit: $7,500).
Brackets, limits, and IRMAA thresholds verified against IRS and SSA publications as of April 2026. Confirm your specific situation with a specialist.
When is the best time to do a Roth conversion?
The optimal window is between retirement and RMD age — the "golden window." Most retirees retire around 60-65 while RMDs begin at 73 (born 1951-1959) or 75 (born 1960+). Earned income has stopped, Social Security may not have started, and the federal bracket is often 12-22% — far lower than the 32%+ effective rate RMDs impose once combined income surges. See the golden window guide for a detailed timeline.
How much can I convert to Roth IRA each year?
There is no IRS annual dollar limit on Roth conversions. The practical ceiling is your current bracket top: for a couple with $60,000 in other income, the 2026 22% ceiling allows about $141,000 in conversions ($201,050 − $60,000). IRMAA Tier 1 ($218,000 MFJ) and ACA subsidy cliffs (pre-65) impose additional ceilings. Use the bracket calculator to find your personal ceiling.
Does a Roth conversion count as income for Medicare IRMAA?
Yes. Conversions add to MAGI and IRMAA uses a two-year lookback — a 2026 conversion affects 2028 Medicare premiums. Tier 1 begins at $109,000 single / $218,000 MFJ, adding $1,148/yr per person. Specialists either keep conversions just below tier thresholds or confirm that crossing a tier still saves money given the lifetime tax differential. Use the IRMAA calculator to check your situation.
Is a Roth conversion worth it?
The conversion wins when your current rate is meaningfully lower than future RMD rates. At 22% now vs. 32% later, every dollar converted saves $0.10 — compounding tax-free for 15-25 years. For a $1.5M IRA converted over 8 years, lifetime savings run $300-500K at typical assumptions. The math weakens when current and future rates are similar, when there are no outside funds to cover the tax bill, or when the planning horizon is short. See the is it worth it decision guide for a full framework.
What is the 5-year rule on Roth conversions?
Each Roth conversion carries its own 5-year holding period before the converted amount can be withdrawn penalty-free — but only if you are under 59½. Once you are 59½ or older, the per-conversion 5-year clock does not apply to withdrawals of converted principal. For most retirees in the 60-73 golden window, this rule is irrelevant in practice. See the 5-year rule guide for both rules explained in full.
Should I convert before or after starting Social Security?
Before, in most cases. Social Security adds up to 85% of your benefit to taxable income (IRC § 86), and in the phase-in zones conversions carry a 1.5×–1.85× effective tax multiplier. Converting in years before SS starts — when ordinary income is lowest — is almost always more efficient. See the SS + Roth conversion interaction guide for the mechanics.
Related reading
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