Roth Conversions vs. ACA Subsidies: The Impossible Tradeoff

If you retire before 65 and rely on ACA Marketplace health insurance, you face one of the sharpest tradeoffs in personal finance: Roth conversions save you tens of thousands in future taxes, but they increase your MAGI today — potentially pushing you off the ACA subsidy cliff and costing you $10,000–$25,000 in a single year.

There is no easy answer. But there is a framework for making the right decision based on your specific numbers. This article walks through the mechanics, provides case studies at three income levels, and identifies the scenarios where each side of the tradeoff wins.

The Core Tension

Roth conversions move money from a Traditional IRA (or 401k) into a Roth IRA. You pay income tax on the converted amount now, but all future growth and withdrawals from the Roth are tax-free.[2]

The benefits of converting are significant and well-documented:

• Reduces future Required Minimum Distributions (RMDs), which begin at age 73
• Lowers future exposure to the Social Security tax torpedo[4]
• Reduces future IRMAA surcharges on Medicare premiums[6]
• Creates a pool of tax-free income that does not affect MAGI
• Provides tax diversification in an uncertain future tax environment

The problem: every dollar you convert is added to your MAGI for the current year. For ACA purposes, MAGI determines your premium tax credit. If the conversion pushes your MAGI above 400% of the Federal Poverty Level, you lose the entire subsidy — not just the portion attributable to the conversion.[1]

With the ACA subsidy cliff back in effect for 2026, a 60-year-old couple in a moderate-cost area might face a subsidy worth $18,000/year. A Roth conversion that pushes them $1 over the cliff would cost $18,000 in lost subsidies plus the income tax on the conversion itself. That is an effective tax rate that can exceed 70% on the marginal dollar.

A Framework for Deciding

The decision comes down to comparing two numbers:

1. The cost of converting this year — income tax on the conversion amount, plus the value of any ACA subsidies lost, plus any IRMAA surcharges triggered (if within 2 years of Medicare).
2. The cost of NOT converting — the future tax on that money when it comes out as RMDs, including the torpedo tax, IRMAA surcharges, and potential NIIT triggered by higher future income.

If the cost of converting now (including lost subsidies) is less than the present value of future taxes avoided, converting wins. If the subsidies you would lose exceed the future tax savings, preserving subsidies wins.

The variables that matter most:

• Years until Medicare — More years = more years of lost subsidies = higher cost of converting
• Traditional IRA balance — Larger balance = larger future RMDs = higher cost of NOT converting
• Current tax bracket — Lower bracket now = cheaper to convert now
• Expected future bracket — Higher expected future bracket = more valuable to convert now
• ACA subsidy value — Larger subsidy = higher cost of converting

Case Study 1: The Early Retiree With a Large IRA

Profile: Sarah, age 58, single. Retired with a $900,000 Traditional IRA and $200,000 in a taxable brokerage. No Social Security yet. Base income (dividends and interest) of $15,000/year. In a moderate-cost ACA market.

The cliff:At 400% FPL for a household of one, Sarah's cliff is approximately $62,600.[5] Her ACA subsidy is worth about $12,000/year at her age and location.

Without conversions: Sarah preserves her $12,000 annual subsidy for 7 years (until Medicare at 65), saving $84,000 in subsidies. But her IRA grows to roughly $1.3M by age 73, generating RMDs of $50,000+ that land squarely in the Social Security torpedo zone and trigger IRMAA.

With partial conversions: Sarah converts $47,000/year (bringing MAGI to ~$62,000, just under the cliff). She pays approximately $5,600 in federal tax per year on the conversion (12% bracket for most of it). Over 7 years, she converts $329,000, paying roughly $39,200 in total conversion taxes. She keeps her full ACA subsidy every year.

Result: Partial conversions are the clear winner. Sarah reduces her future IRA balance by $329,000, dramatically lowering RMD-era taxes, while preserving every dollar of ACA subsidy. The key insight: she does not have to choose between converting and keeping subsidies — she converts up to the cliff and stops.

Case Study 2: The Couple Near the Cliff

Profile: David and Maria, both 62, married filing jointly. Combined Traditional IRAs of $600,000. Pension income of $30,000/year. Part-time consulting income of $25,000/year. In a high-cost ACA market.

The cliff: For a household of two, 400% FPL is approximately $84,600.[5] Their ACA subsidy is worth $22,000/year given their ages and location.

The problem: Their base MAGI is already $55,000 ($30,000 pension + $25,000 consulting). They have only $29,600 of headroom before the cliff. Any Roth conversion competes with that narrow window — and with only 3 years until Medicare, the subsidy preservation value is $66,000 ($22,000 x 3 years).

With conversion: Converting $29,000/year (staying just under the cliff) for 3 years moves $87,000 to Roth. Conversion tax: roughly $10,400 total (22% bracket on the upper portion). They keep their full subsidy.

With aggressive conversion over the cliff: Converting $80,000/year moves $240,000 to Roth over 3 years but costs $66,000 in lost subsidies plus roughly $36,000 in conversion taxes = $102,000 total cost.

Result: For this couple, the math strongly favors preserving subsidies and doing modest partial conversions. The $22,000/year subsidy dwarfs the incremental tax savings from converting more aggressively. They are better off converting the remaining IRA balance after they transition to Medicare at 65, when conversions no longer affect ACA subsidies.

Case Study 3: The Young Retiree With a Long Runway

Profile: James, age 50, single FIRE retiree. Traditional IRA of $1.2M. Taxable portfolio of $800,000. Dividend/interest income of $20,000. No earned income. 15 years until Medicare.

The cliff: 400% FPL for a household of one is approximately $62,600.[5] ACA subsidy at age 50 in a moderate market: approximately $8,000/year.

The long game: If James does no conversions, his $1.2M IRA could grow to $2.4M+ by age 73 (at 5% annual growth). His RMDs would start at roughly $96,000/year, creating massive torpedo exposure, IRMAA surcharges, and potential NIIT exposure.

Converting over the cliff: James converts $80,000/year, bringing MAGI to $100,000. He loses his $8,000 ACA subsidy each year. Over 15 years, that is $120,000 in lost subsidies. But he converts $1.2M to Roth, paying approximately $156,000 in conversion taxes (blended 13% rate). Total cost: $276,000.

Without converting:At age 73, James faces RMDs taxed at 22–24% (or higher), torpedo-inflated rates of 40%+, annual IRMAA surcharges of $2,000+, and potential NIIT of $3,800+/year. The present value of these future taxes easily exceeds $400,000.

Result: With 15 years of compounding and a large IRA, converting over the cliff wins decisively. The $8,000/year subsidy loss is real, but it is far outweighed by the future tax savings. James should also explore whether he can reduce base MAGI (tax-loss harvest the taxable portfolio) to convert more while keeping some subsidy.

When to Prioritize Roth Conversions

• Large Traditional IRA balance ($500K+ single, $800K+ married) — Future RMDs will be substantial, creating torpedo, IRMAA, and NIIT exposure.
• Many years until Medicare (8+ years) — More time means more years of tax-free compounding in the Roth, which increases the payoff.
• Low current tax bracket— Converting in the 10–12% bracket is a bargain compared to future RMDs in the 22–24% bracket (plus torpedo effects).
• ACA subsidy is relatively small — Younger enrollees, healthy individuals, or those in low-cost ACA markets have less to lose from crossing the cliff.

When to Prioritize ACA Subsidies

• Close to Medicare(1–3 years) — The subsidy window is short and finite. Preserve it; you can convert aggressively after 65.
• Modest Traditional IRA balance — If future RMDs will be small and manageable, the urgency to convert is low.
• High-value subsidy— Older enrollees (60–64) in high-cost markets may have subsidies worth $20,000+/year. That is extremely expensive to sacrifice.
• Already near the cliff — If your base MAGI is within $5,000 of 400% FPL, even a small conversion pushes you over. The marginal cost per dollar converted is extreme.

The “Gap Years” Strategy

The most effective approach for many early retirees is not to choose between conversions and subsidies, but to optimize both across the gap years — the period between retirement and Medicare/Social Security.[3]

The strategy has three phases:

1. Phase 1 — Pre-Medicare, pre-Social Security (e.g., ages 55–64): Convert up to the ACA cliff each year. Fill every dollar of headroom between your base MAGI and 400% FPL with Roth conversions. You get both: subsidies AND conversions.
2. Phase 2 — On Medicare, pre-Social Security (e.g., ages 65–69): The ACA cliff no longer applies. Convert more aggressively, limited only by IRMAA tiers (which have higher thresholds) and your target tax bracket.[6]
3. Phase 3 — On Medicare, receiving Social Security (age 70+): Conversion space shrinks because Social Security adds to MAGI. But if Phase 1 and 2 reduced your Traditional IRA sufficiently, RMDs are manageable and the torpedo is avoided.

The gap years strategy recognizes that the ACA subsidy cliff is temporary — it only matters during the years you are on Marketplace coverage. IRMAA and the torpedo are permanent concerns that persist for the rest of your life. Plan accordingly.

The Bottom Line

The Roth-vs.-ACA tradeoff is not a binary choice. The optimal strategy for most early retirees is partial conversions up to the cliff — capturing the tax-arbitrage benefits of Roth conversions while preserving every dollar of ACA subsidy. Only when the Traditional IRA balance is very large and the subsidy value is relatively small does it make sense to deliberately convert over the cliff.

Run the numbers for your specific situation using the calculators below. Small differences in age, IRA balance, subsidy value, and years to Medicare can flip the answer. And if the numbers are close, consider consulting a fee-only financial planner who specializes in early retirement tax planning — the stakes are high enough to warrant professional analysis.