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 (approximate, MFJ):

• 10% bracket ends at $23,850
• 12% bracket ends at $96,950
• 22% bracket ends at $206,700
• 24% bracket ends at $394,600
• 32% bracket ends at $501,050

For a couple with $60K of non-conversion income, converting $146K tops off the 22% bracket precisely. Annual re-calibration matters — each year your other income shifts.

IRMAA — the hidden cliff

Medicare Part B + D premiums surcharge above income thresholds. 2026 single thresholds approximately:

• Tier 1: $106K+ MAGI → +$82/mo premium
• Tier 2: $133K+ → +$206/mo
• Tier 3: $167K+ → +$329/mo
• Tier 4: $200K+ → +$453/mo
• Tier 5: $500K+ → +$495/mo

Thresholds double for MFJ. A conversion that bumps you into a higher tier adds $1,000-6,000/yr of Medicare premiums — an unexpected tax increase you didn't plan for. Specialists keep conversions just below threshold edges.

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). Separate from the 5-year rule on Roth IRA contributions. For retirees 59½+ already, doesn't apply to withdrawals of converted funds. 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. You can't cherry-pick "just the after-tax portion" to convert. Track basis on Form 8606 annually. For those with meaningful basis: consider IRA-to-401(k) rollover to isolate the pre-tax portion, then convert the after-tax cleanly.

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.