Week 42 Day 5: Roth Conversions: Paying Tax Now to Avoid It Later

You have $100,000 in a traditional IRA. You convert $20,000 to a Roth this year. You pay approximately $4,400-$7,400 in income tax (at 22-37% rate). But that $20,000 now grows tax-free. In 20 years at 10%, it becomes $134,000 -- all tax-free. Without the conversion, you would owe approximately $29,000-$50,000 in tax on that $134,000 at withdrawal. The conversion saved $24,600-$42,600.

When Roth conversions make sense: (1) Low-income years. If you lose your job, take a sabbatical, or retire early before Social Security starts, your income (and tax rate) may be temporarily low. Convert enough traditional IRA money to fill the low tax brackets (10%, 12%, 22%). You pay a low rate today on money that would have been taxed at a higher rate later. (2) Early retirement bridge. Between retirement (55-60) and Social Security (67-70), your income may be very low. This is the 'Roth conversion window' -- potentially 7-15 years of low-income opportunity to convert traditional money to Roth at favorable rates. (3) Before Required Minimum Distributions (RMDs). At age 73 (under current law), you MUST withdraw from traditional IRAs whether you need the money or not. Large traditional IRA balances create large RMDs, pushing you into higher tax brackets. Converting before 73 reduces the traditional balance and future RMDs. (4) If you believe tax rates will increase. Current tax rates (2025) are historically low. The 2017 Tax Cuts and Jobs Act provisions expire after 2025, potentially increasing rates. Converting now locks in the current low rates. When conversions do NOT make sense: (a) If your current tax rate is higher than your expected retirement tax rate. (b) If you need the conversion money within 5 years (Roth 5-year rule applies to conversions). (c) If the conversion pushes you into a much higher bracket, triggering Medicare surcharges (IRMAA) or loss of other benefits. The optimal strategy: 'bracket filling.' Calculate the top of your current tax bracket. Convert enough traditional IRA money to fill the bracket, but not so much that you jump to the next bracket.

The Roth conversion optimization is a multi-year dynamic programming problem: the decision to convert in year T depends on current and future tax rates, portfolio growth expectations, Social Security claiming strategy, RMD schedule, state tax rates, Medicare IRMAA thresholds, and estate planning goals. Kitces and Pfau (2014) showed that strategic Roth conversions during the early retirement 'gap years' (between retirement and Social Security/RMDs) can increase after-tax retirement wealth by 10-20% relative to no-conversion strategies. The key variable: the marginal tax rate spread between the conversion year and the withdrawal year. If you convert at 22% and would have withdrawn at 32%, the marginal benefit is 10 percentage points on every dollar converted. The break-even analysis: if the conversion tax rate equals the future withdrawal tax rate, the outcome is approximately breakeven (the Roth's tax-free growth exactly offsets the forgone growth on the dollars used to pay the conversion tax). The Roth wins when: (a) future rates exceed current rates, (b) investment returns are high (more tax-free growth), or (c) the conversion tax is paid from non-IRA assets (preserving the full converted balance to grow tax-free). The Roth loses when: (a) future rates are lower than current rates, (b) investment returns are low (less benefit from tax-free growth), or (c) the conversion pushes income into higher brackets, triggering phase-outs and surcharges. For most early retirees with moderate traditional IRA balances ($200K-$1M), a systematic annual Roth conversion filling the 22% or 24% bracket is near-optimal and far preferable to the default strategy of no conversion.