Roth conversions before 65 have a hidden second price

If you retire before 65, health insurance comes from the individual market — and the premium tax credit (PTC) that makes it affordable is means-tested. That turns a Roth conversion into a two-part transaction. The IRS explains the basics of who qualifies for the credit.

What changed for 2026

Two changes have reset the rules this post describes. First, the enhanced premium tax credits expired on December 31, 2025, so the hard subsidy cliff at 400% of the federal poverty line is back for 2026 — cross it, and the credit can drop to zero.

Second, the caps on repaying excess advance credits are gone for tax years after 2025. If your income comes in higher than you estimated, you repay the full excess; the IRS explains the current rule in its premium tax credit questions and answers. Both changes make sizing a conversion more important, not less.

The visible part

A Roth conversion moves money from a traditional IRA or 401(k) into a Roth account. You pay ordinary income tax on the converted amount now, and qualified distributions grow tax-free afterward. If you're in a low bracket in early retirement, filling that bracket with conversions is one of the most reliable moves in the toolkit.

The appeal is real: low-income years between retirement and required minimum distributions are often the cheapest time you'll ever have to shift dollars into Roth. Future RMDs shrink, surviving-spouse single-bracket years get easier, and heirs inherit cleaner accounts. But before 65, every converted dollar also flows into a second calculation.

The hidden part: what counts toward the subsidy

Eligibility for the credit is based on household income — roughly your modified adjusted gross income plus tax-exempt interest, excluded foreign income, and nontaxable Social Security. Critically, the full amount of a Roth conversion counts. There is no adjustment or exclusion for it.

HealthCare.gov shows how advance payments of the credit lower your monthly bill — and must be reconciled at tax time. The flow works like this:

1. You estimate income when you enroll, and the marketplace pays part of your premium in advance (APTC) based on that estimate and the benchmark Silver plan in your area.
2. You reconcile at filing. You claim the final credit and square it against the advance payments on Form 8962, Premium Tax Credit.
3. Too much advance credit means repayment. If your final income comes in higher — say because of a December conversion you didn't report — you repay the excess with your tax return. For tax years after 2025 there is no repayment cap, so the full excess is repayable; the only narrow exception is if final income ends up below 100% of the federal poverty line with no intentional misreporting. The IRS covers the current rule in its premium tax credit questions and answers.

So a conversion does double duty: it raises the income tax on the return and shrinks (or repays) the subsidy for the same year.

Why the marginal rate spikes

In the range where the credit phases out, the marginal cost compounds:

• Federal income tax: say 12% or 22%
• Plus lost subsidy: meaningful additional cents per dollar, rising as you approach the cliff

In the 300–400% band near the top of the subsidy range, add them together and a conversion that looks like a 22% decision can behave like a 30%+ decision — which may still be worth it, but only if you can see the full number.

Three details determine how large that second charge is:

• It's tied to the benchmark plan, not your plan. The credit is calculated off the second-lowest-cost Silver plan in your rating area. Older households and high-premium regions face larger credits — and therefore larger phase-out penalties per extra dollar — than younger households in cheap regions.
• Silver-plan cost-sharing reductions are a second tripwire. Lower-income marketplace buyers can also get reduced deductibles and copays, but only on Silver plans. Convert just over that tier's income limit and you lose richer cost-sharing on top of the premium credit.
• The top of the subsidy range is a hard edge. Cross the top income band and the credit can fall to zero. A conversion sized without accounting for that can cost far more than the tax bracket suggests — thousands of dollars for a few hundred dollars of extra conversion income.

Timing and coordination matter more than conviction

Conversions before 65 are rarely "always" or "never" — they are a sizing problem. Practical patterns that work:

• Convert to the cliff, not through it. Measure headroom to the next subsidy threshold the way you'd measure headroom to the next bracket, and stop the conversion just short of the expensive line.
• Fund living expenses from low-MAGI sources in high-subsidy years. Cash, taxable-account principal (rather than gains), HSA dollars for medical costs, and Roth contributions already available tax-free can cover spending without adding conversion income on top.
• Don't stack income events. A conversion plus a large capital-gain realization, a year-end bonus payout, or unexpected mutual-fund distributions can combine to breach a threshold none of them would breach alone.
• Report income changes promptly. Updating your marketplace application mid-year when income rises lets you trim advance payments and avoid a repayment surprise; when income falls, it raises your advance credit and lowers monthly premiums sooner.
• Plan the age-65 handoff. Marketplace coverage ends when Medicare begins, but the IRMAA clock starts at 63. Heavy conversions at 63–64 can therefore cost you twice: less subsidy now, higher Medicare premiums at 65–66. Many households convert more aggressively before 63 or after the subsidy years, and more surgically during them.

Also watch the interaction with the 0% capital-gains threshold and the Social Security taxation hump. All three — subsidy phase-out, capital-gains stacking, and taxable Social Security — key off the same extra dollar, so the true marginal cost is the sum, not any single bracket rate.

How to see it

The useful question isn't "what bracket am I in?" It's "what does the next dollar actually cost?" The RetireTaxGuide tax planner stacks federal tax, lost ACA subsidy, IRMAA, and the Social Security tax torpedo into a single marginal-cost view, with the cliffs marked. That lets you size a conversion to stop just short of the expensive line instead of guessing — modeling Roth conversions, capital gains, and IRA withdrawals side by side and watching the whole year as a tax-flow diagram.

Educational only — not tax or financial advice. Subsidy rules have changed repeatedly; verify current law in the IRS's premium tax credit overview and at HealthCare.gov before acting.