How to Handle ACA Auto-Reenrollment for the 2027 Plan Year: Why Doing Nothing Could Still Cost You Hundreds Even After the Court-Stayed CMS Rule

Auto-reenrollment is the ACA marketplace's quiet default. You carried a plan through 2026, you don't log in during open enrollment, and on January 1 the exchange moves you forward into something that resembles the plan you had — same company, usually, with your prior tax credit reapplied. For a lot of consumers in prior years, that default worked fine. For the 2027 plan year, it probably won't.

The 2027 open enrollment that runs November 1 through December 15, 2026 is the first since the enhanced premium tax credits expired at the end of 2025. The 400% federal poverty level subsidy cliff is back. Insurers filed a median 15% rate increase for 2027 on top of the roughly 20% jump already baked into 2026 premiums. And HealthCare.gov is sending a different set of notices this year because a 2026 CMS rule that would have reshaped auto-reenrollment was stayed by a federal court and will not take effect for 2027 either. This is what actually happens if you let the default run, which parts of the CMS rule still show up in your inbox, and the five minutes of work that keeps a stale subsidy from eating your January paycheck.

If you have marketplace coverage on December 15, 2026 and have not actively re-selected a plan for 2027, HealthCare.gov (or your state exchange) does three things on your behalf:

1. Rolls you forward into your 2026 plan if the issuer is offering the same plan for 2027. If the plan was discontinued, the exchange "crosswalks" you to a similar plan from the same issuer, or (if the issuer left the market) to a comparable plan from a different issuer in your rating area.
2. Reapplies your most recent advance premium tax credit against the 2027 benchmark silver premium in your area. Your household size and income are copied from your current application — not updated to a projection.
3. Sends you a Marketplace Open Enrollment Notice in October explaining what will happen and what your 2027 monthly premium is projected to be. The notice assumes everything in your current application is still accurate.

The three traps in that process — a stale subsidy against a new benchmark, a plan crosswalk based on general characteristics rather than your actual care, and an application that may no longer match your situation — are what we unpack below.

Advance premium tax credit (APTC) is calculated from two inputs: the benchmark silver premium in your rating area and your "expected contribution," which is a percentage of your household income determined on a sliding scale. Auto-reenrollment carries your old expected contribution forward but recalculates the benchmark against 2027 rates.

With insurers filing double-digit increases on top of 2026's record hikes, the benchmark in most rating areas is materially higher for 2027. That alone doesn't necessarily increase your net premium — a higher benchmark can mean a bigger subsidy if your income percentage is unchanged. But two things in 2027 break that symmetry:

• The expired enhanced subsidies. With the pandemic-era enhancements gone, the "applicable percentage" table reverts to the pre-2021 schedule, and the 400% federal poverty level cliff is back. If your projected income edges above 400% FPL, your subsidy drops to zero regardless of what the benchmark did.
• Benchmark reshuffling. The "benchmark" is the second-lowest-cost silver plan in your rating area, which can change identity every year. If a cheap silver plan entered or exited your area, the benchmark can move independently of your old plan's premium, so the subsidy you receive and the premium you owe can diverge in opposite directions.

Issuers routinely discontinue specific plans at year-end, add new ones, and sometimes exit a county or rating area entirely. The marketplace responds with a crosswalk: an administrative mapping from your 2026 plan to the 2027 plan that most closely resembles it on paper.

The crosswalk considers metal tier, carrier, HMO vs. PPO structure, and premium range. It does not consider:

• Whether your current primary care doctor is in the 2027 network.
• Whether your current specialists are in the 2027 network.
• Whether your current prescriptions are on the 2027 formulary at the same tier.
• Whether the 2027 plan has prior authorization or step therapy requirements that your 2026 plan did not.

In quiet years the crosswalk often lands close enough. For 2027, with issuers reconfiguring networks and formularies in response to the subsidy environment, it's less reliable. If your October notice says "we are enrolling you in Plan X for 2027," open HealthCare.gov, pull the 2027 version of Plan X, and verify your doctors and drugs one by one. Five minutes of work; months of saved copays.

Marketplace applications persist. The income you projected two Novembers ago, the household size you listed, the address you entered — those stay in place until you update them. Auto-reenrollment pulls directly from the current application.

Before December 15, log into HealthCare.gov and check four things against reality:

1. Projected 2027 modified adjusted gross income (MAGI). This is the single biggest driver of your subsidy. A promotion, a side-business income shift, a spouse's new W-2, a Roth conversion done in 2026 — any of these can move the needle. Underestimate and you owe the IRS at tax time; overestimate and you leave money on the table all year.
2. Household size. The people you'll claim as tax dependents on your 2027 return. New baby? Child aged out at 26? Spouse now on Medicare? Each of these changes the household count and the subsidy.
3. Address and county of residence. Rating areas are drawn by county. A move within the same state can change your benchmark, your plan availability, and your subsidy.
4. Immigration or coverage-eligibility status. If anyone in the household gained or lost eligibility — for example, became a lawful permanent resident, aged into Medicare, or started a job that offers employer coverage — the application needs to reflect it.

CMS finalized two auto-reenrollment changes for the 2026 plan year that got significant attention and then significant pushback:

• A rule requiring consumers auto-reenrolled into a $0-premium plan to pay $5 per month until they updated their application and re-verified eligibility.
• A related rule requiring consumers with a $0 premium in the current plan year to actively update their application in order to re-qualify for a $0 premium for the next year.

Both rules were challenged in federal court. In City of Columbus v. Kennedy, a federal district court stayed the $5 auto-reenrollment rule, and CMS has confirmed in its Updated Federal Standard Notices and Enforcement Safe Harbor guidance for Plan Year 2027 that the stayed changes will also not apply for the 2027 benefit year.

Translation for consumers: if you had a $0-premium plan in 2026 and auto-reenroll into the same plan for 2027, you are not automatically moved to a $5 premium by the stayed rule. However, the actual premium of your plan can still change for 2027 based on the issuer's rate filing and the new benchmark, so a "$0 in 2026" plan is not guaranteed to be "$0 in 2027." Read your October notice carefully and verify the 2027 premium figure.

Notices to expect in October 2026

• A Marketplace Open Enrollment Notice describing your 2027 projected premium, subsidy, and plan assignment.
• An issuer renewal notice from your insurance company describing any plan or benefit changes.
• If applicable, a plan discontinuance or crosswalk notice explaining the specific plan you will be rolled into if your 2026 plan is not being offered.

None of those notices do the one thing that actually protects you: a plan-by-plan comparison based on your projected 2027 income and your actual care needs.

If you want to prevent surprises, treat auto-reenrollment as a safety net rather than a plan. Between November 1 and December 15, 2026, do the following:

1. Log into HealthCare.gov (or your state marketplace). Update projected 2027 MAGI, household size, address, and employer coverage availability.
2. Shop with the updated application. The marketplace recalculates your subsidy against 2027 benchmarks using your updated inputs. Compare the top three or four plans by total expected cost (premium + expected deductible + expected out-of-pocket for your actual care).
3. Check networks and formularies one by one. Primary care doctor, specialists, hospital, prescriptions. The plan's "Find a doctor" and "Find a drug" tools on the marketplace are decent; the issuer's own portal is more current.
4. Confirm cost-sharing reductions (CSR) silver tiers. If your income is between 100% and 250% FPL, CSR silver plans still carry the lower deductibles and copays they did in prior years. CSR benefits are tied to income, not plan name — you have to actively enroll in a silver plan to receive them. Auto-reenrollment into a bronze plan forfeits the CSR, even if the subsidy dollars look similar at first glance.
5. Actively select the plan and confirm the January 1, 2027 start date before December 15.

Even if you missed the November-15 flag, you still have running room. On HealthCare.gov the full federal open enrollment window closes December 15, 2026 for a January 1 start. Many state-based marketplaces extend into January; check your state's deadline. Within those windows, changing plans takes effect the first of the following month.

After open enrollment closes, you can only switch plans with a Special Enrollment Period triggered by a qualifying life event: moving to a new county or state, losing other coverage (including Medicaid), getting married, having a baby, adoption, or a few others. Learning that your crosswalked plan doesn't cover your doctor is not itself a qualifying event.

Auto-reenrollment for the 2027 plan year isn't broken, but it is doing exactly what it did last year on top of a materially different market: a subsidy environment without the enhanced tax credits, a benchmark pushed higher by double-digit rate hikes, and plan crosswalks that don't check whether your doctor and drugs still fit. The CMS $5-premium rule and the $0-premium reverification rule that could have made all of this louder are stayed by court order and won't apply in 2027, so you won't see those changes in your October notice — but the underlying premium shift is still there. Twenty minutes on HealthCare.gov between November 1 and December 15, with your projected 2027 MAGI, your doctor list, and your prescription list in hand, is enough to override the default. If you miss the window and your January premium or network looks wrong, you have federal open enrollment through December 15 (longer in some state marketplaces) to switch; after that it's special-enrollment territory, and realizing the plan isn't right doesn't qualify by itself.