Open enrollment for 2027 Affordable Care Act coverage begins November 1, 2026 and ends December 15 on the federal exchange — a month earlier than the January 15 deadline retirees have grown used to, under the CMS Marketplace Integrity and Affordability rule finalized last year. State-based marketplaces may set their own dates but must start by November 1, end no later than December 31, and run no longer than nine weeks.
The shortened window is the smaller of two changes. The larger one is that a threshold most early retirees stopped worrying about five years ago is back.
It's a Cliff, Not a Slope
The enhanced premium tax credits created by the Inflation Reduction Act expired at the end of 2025, and Congress did not extend them in the One Big Beautiful Bill Act. That restores the ACA's original structure: above 400% of the federal poverty level, the premium subsidy is not reduced — it is zero.
Subsidy eligibility runs on a one-year lag. Your 2027 coverage is measured against the FPL guidelines announced in January 2026, which put 400% FPL in the 48 contiguous states at $63,840 for a household of one and $86,560 for a household of two.
KFF modeled a couple in their early 60s in Kaukauna, Wisconsin with an income of $85,000. Their monthly premium goes from $602 to $2,144 — a 250% increase. Note where that couple sits: roughly $1,500 below the line. A modest year-end traditional IRA withdrawal would push them over it and cost them the entire remaining credit.
Premiums Are Rising Into the Cliff
The median proposed 2027 rate increase across 276 insurers is 15%, per the Peterson-KFF Health System Tracker — a second consecutive double-digit year after 2026's 18% proposed and 20% finalized increases. Insurers attribute a median 10% to medical trend, citing provider contract increases, economy-wide inflation, healthcare labor shortages, GLP-1 drug costs, and a risk pool that deteriorated as healthier enrollees dropped coverage. One Indianapolis enrollee above 400% FPL faces a 41% cumulative increase over two years.
Higher gross premiums make the subsidy below the line larger — which makes crossing the line more expensive, not less.
ACA MAGI Is Not the MAGI You Know
This is where retirement accounts enter the picture. MAGI is defined differently for every program, and the ACA version is AGI plus tax-exempt interest, plus the non-taxable portion of Social Security benefits, plus foreign earned income exclusions.
Two traps follow. Municipal bond interest never touches AGI but does count here. And the full Social Security benefit counts — including the portion that isn't taxable.
Raises ACA MAGI: traditional IRA and 401(k) withdrawals, Roth conversions (the entire converted amount), realized capital gains, dividends, interest.
Does not: qualified Roth distributions, return of principal from a taxable brokerage account, HSA distributions for qualified expenses.
Practical Takeaways
Know your line before December. Project full-year MAGI against $63,840 or $86,560 while you still have time to act.
Sequence withdrawals deliberately. Retirees holding both Roth and traditional balances have genuine control over which side of the cliff they land on. Drawing the marginal dollar from a Roth account or from taxable-account basis is invisible to ACA MAGI.
Reprice your Roth conversions. Filling low tax brackets during the pre-Medicare gap years is standard advice, but a conversion that crosses 400% FPL can forfeit more in subsidy than it saves in lifetime tax. Run the arithmetic before converting.
Remember the handoff at 65. Medicare replaces the subsidy cliff with IRMAA — a different threshold, on a two-year lookback. The income year you are managing now still matters later.
Sources: Peterson-KFF Health System Tracker – How much and why ACA Marketplace premiums are going up in 2027; KFF – ACA Marketplace Premium Payments Would More than Double on Average Next Year if Enhanced Premium Tax Credits Expire; The Finance Buff – 2026/2027 Federal Poverty Levels for ACA Health Insurance; CMS – 2025 Marketplace Integrity and Affordability Final Rule; HealthCare.gov – Modified Adjusted Gross Income (MAGI) glossary