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Open enrollment is the one window each year when you can change your health plan, and the mistakes people make during it are expensive in a quiet way. Nobody gets a bill labeled “open enrollment mistake.” They just pay more every month, or discover in March that their doctor is out of network. These are the errors that cost real money.
Mistake 1: letting your plan auto-renew without looking
Most marketplace and employer plans renew automatically if you do nothing. That feels convenient, and sometimes the renewal is fine. But plans change every year: premiums move, deductibles move, networks change, and drug formularies get rewritten. A plan that was the best deal last year can be a mediocre one this year without you noticing. Every open enrollment, treat your current plan as a stranger and compare it against the new options from scratch.
Mistake 2: comparing premiums instead of total cost
The monthly premium is the most visible number and the least complete one. Two plans can differ by a modest amount per month and differ by thousands per year once you add the deductible, copays, and out-of-pocket maximum. The honest comparison is premiums plus expected cost sharing for the year. A plan with a slightly higher premium and a much lower deductible often wins for anyone who uses care regularly. Do the full-year math for a good year and a bad year before you decide.
Mistake 3: not checking whether your doctors are still in network
Networks change every year, and provider directories are often out of date. The cost of assuming your doctor is covered can be the full price of out-of-network care, which may not count toward your deductible at all. Before you enroll, call each doctor’s office you care about and ask which plans they will accept next year. Do the same for your pharmacy and any hospital you would use. This takes an afternoon and prevents the most common enrollment regret.
Mistake 4: ignoring the prescription drug formulary
If you take any regular medication, the formulary, the list of covered drugs and their tiers, matters as much as the premium. A drug that moves from a low tier to a high tier, or off the formulary entirely, can add a large monthly cost that no premium comparison will show. Check every medication you take against each plan’s formulary, including the tier and any prior authorization requirement. If you take a specialty drug, look specifically at the coinsurance rate for that tier, because a percentage of a very expensive drug adds up fast.
Mistake 5: picking the HSA plan and never funding the HSA
High-deductible plans paired with health savings accounts are often the best deal on the menu, but only if you actually use the account. The lower premium is the visible benefit. The tax savings on contributions are the bigger one, and the account rolls over forever, unlike an FSA. People choose the HDHP for the cheap premium and then leave the HSA empty, which means they took the higher deductible without capturing the reward. If you choose this route, set up automatic contributions on day one. Our HSA versus PPO breakdown shows how to run the comparison properly.
Mistake 6: missing subsidies and tax credits you qualify for
On the marketplace, premium tax credits are based on your estimated income for the coverage year, not last year’s tax return. People who got a raise, changed jobs, or had a change in household size often qualify for a different subsidy than the year before, in either direction. Estimate your income carefully. Underestimate it and you may owe money back at tax time. Overestimate it and you leave monthly savings on the table. If your income changed, update the application rather than letting last year’s numbers ride.
Also check whether you qualify for cost-sharing reductions, which lower deductibles and out-of-pocket costs on silver plans for eligible incomes. These are separate from premium credits and easy to miss.
Mistake 7: forgetting life changes that create special enrollment rights
Open enrollment is not the only way in. Marriage, divorce, the birth or adoption of a child, losing other coverage, and moving to a new area all trigger special enrollment periods, usually 60 days. People who miss open enrollment often assume they have to wait a full year, and people who experience a qualifying event often do not realize the clock is ticking. If anything major changed in your life, check whether it opens a window before you settle for going uninsured.
When open enrollment happens
For the federal marketplace, open enrollment typically runs from November 1 through mid-January, with coverage starting January 1 for plans selected by the December deadline. Many states that run their own exchanges follow a similar calendar with their own deadlines, and employer open enrollment usually falls somewhere in the fall, set by each company. Mark your specific deadlines, because missing them generally means waiting a year unless you qualify for special enrollment.
If you are shopping the marketplace and want a sense of what plans cost, our guide to monthly health insurance costs breaks down the price drivers by tier.
A simple enrollment checklist
When your window opens, work through these in order. First, confirm your doctors, pharmacy, and hospital are in network for each plan you are considering, by calling, not just by checking the directory. Second, check your prescriptions against each formulary. Third, add up the full-year cost, premiums plus expected cost sharing, for a good year and a bad year. Fourth, update your income estimate if you are on the marketplace. Fifth, if you are choosing a high-deductible plan, set up HSA contributions immediately.
Open enrollment rewards the people who do the homework. The plans do the math in their favor by default. An hour of comparison shopping is one of the highest-paid hours of your year.
