This article is for general educational purposes and is not tax, legal, or medical advice; unless noted inline, all federal contribution figures reflect the 2026 plan year and all employer-market averages reflect KFF’s 2025 survey.
TL;DR — Quick Verdict
- Auto-renewing without re-comparing is the single most expensive mistake: the average employer family premium hit $26,993 in 2026, and workers already pay $6,850 of that (KFF).
- The 2026 health FSA limit is $3,400 and it is use-it-or-lose-it; over-funding by even $500 hands that money back to your employer.
- An HDHP paired with the 2026 HSA ($4,400 individual / $8,750 family) often beats a low-deductible PPO on total annual cost — but only if you run the break-even math.
- ACA Marketplace shoppers face a different world in 2026: enhanced premium tax credits expired December 31, 2025, roughly doubling the average subsidized net premium.
- Recommendation: treat open enrollment as an active purchase decision — model your expected total cost across two plans before you click “keep current coverage.”
Roughly nine in ten workers re-enroll in the exact same health plan they had last year, and most never open the comparison tool. That inertia is expensive. The average annual premium for employer-sponsored family coverage reached $26,993 in 2026, with workers contributing $6,850 of it out of their own paychecks, according to KFF’s 2025 Employer Health Benefits Survey. When your plan’s network, drug formulary, or deductible shifts underneath you — which happens quietly every year — “keeping what I had” is rarely the same plan you actually had.
This guide walks through the specific, dollar-quantified mistakes people make during open enrollment: over- and under-funding tax-advantaged accounts, misreading the premium-versus-deductible trade-off, and ignoring the seismic 2026 change to ACA subsidies. Whether you enroll through an employer portal like Workday or shop HealthCare.gov directly, the goal is the same — spend fifteen minutes on math and avoid four figures in waste.
Mistake #1: Auto-Renewing Without Recomparing Total Cost
Premiums are only the visible price tag. The number that actually governs your year is total annual cost — premium plus expected out-of-pocket spending under each plan’s deductible and coinsurance. Two plans with a $1,200 premium gap can flip in ranking the moment you add a planned surgery or a chronic prescription.
Here is why re-comparing matters: plan designs drift. An employer can raise your deductible, drop a hospital system from the network, or move your medication to a higher formulary tier — all while keeping the plan’s name identical. If you auto-renew, you inherit every one of those changes without consent. The disciplined move is to pull your prior-year claims total and run it against each plan on offer, a process laid out in our guide to comparing plans beyond the monthly premium.
Source: KFF 2025 Employer Health Benefits Survey (verify at kff.org).
Mistake #2: Over-Funding a Use-It-or-Lose-It FSA
The health flexible spending arrangement is one of the best tax deals in the benefits menu — and one of the easiest to bungle. For 2026 the IRS set the health FSA contribution limit at $3,400, with employers permitted to allow a $680 carryover into the next plan year (IRS Revenue Procedure 2025-32). Everything above that carryover, if your employer offers one at all, evaporates at year-end.
Consider the math on over-funding. A worker in the 22% federal bracket who elects $3,400 but only incurs $2,400 in eligible expenses forfeits $1,000. The tax saving on that contribution was roughly $220; the forfeiture was $1,000. You paid a dollar to save twenty-two cents. Under-funding carries the opposite, smaller cost — you simply lose the tax break on dollars you spent anyway. Because forfeiture dwarfs the missed deduction, the correct posture is to fund the FSA to your reliably predictable spending, not your optimistic maximum. If you also qualify for a health savings account, the FSA versus HSA rules and savings comparison matters, because the HSA has no forfeiture risk at all.
Mistake #3: Rejecting the HDHP Without Doing the HSA Math
“High deductible” sounds like a warning label, so many enrollees skip HDHPs on reflex. That reflex ignores the health savings account, which turns the HDHP into a wealth-building vehicle. For 2026, an HSA-qualifying HDHP must carry a minimum deductible of $1,700 for self-only coverage or $3,400 for family coverage, with out-of-pocket maximums capped at $8,500 and $17,000 respectively (IRS Revenue Procedure 2025-19).
The offsetting advantage is the HSA. You can contribute up to $4,400 (self-only) or $8,750 (family) in 2026, plus a $1,000 catch-up at age 55 or older — and those dollars are triple-tax-advantaged: deductible going in, tax-free growth, tax-free withdrawal for qualified expenses. Employers often sweeten HDHPs with a seed contribution of several hundred to a thousand dollars, effectively pre-funding your deductible. Run the comparison in our HMO, PPO, and HDHP total annual cost comparison before dismissing the option, and if you land on the HDHP, the strategy for maximizing HSA value with a high-deductible plan is where the real money is made.
Source: IRS Revenue Procedure 2025-19 (verify at irs.gov). Catch-up contribution of $1,000 applies at age 55+.
Low-Deductible PPO vs. HSA-Eligible HDHP: Which Is Better for a Healthy Single Filer?
Take a healthy 34-year-old with self-only coverage and no chronic conditions, choosing between a PPO and an HDHP. Assume the PPO costs $1,200 more per year in premium than the HDHP, the HDHP carries a $1,700 deductible, and the employer seeds $500 into the HSA. In a year with only a routine physical (covered as preventive under both), the HDHP wins outright: the enrollee pockets the $1,200 premium difference plus the $500 seed, then shelters up to $4,400 in the HSA, cutting taxable income by that amount.
Flip the scenario to a year with a $6,000 hospital event. The HDHP enrollee pays the $1,700 deductible plus coinsurance up to the $8,500 out-of-pocket cap; the PPO’s lower deductible may limit exposure more tightly. The deciding variable is expected utilization, which is exactly what a plan-selection break-even calculation isolates. The mechanics of how these two ceilings interact are covered in our explainer on deductible and out-of-pocket maximum mechanics.
Verdict
For a healthy single filer with low expected claims, the HSA-eligible HDHP is usually the stronger financial choice — the premium savings, employer seed, and triple-tax HSA advantage compound over time. For someone anticipating a major procedure, expensive medication, or the birth of a child, the low-deductible PPO’s tighter cost-sharing often justifies its higher premium. Decide on projected spending, not the deductible label.
Mistake #4: Shopping the ACA Marketplace as if It Were Still 2025
Anyone buying individual coverage faces a materially changed landscape. The enhanced premium tax credits that had held down Marketplace premiums since 2021 expired on December 31, 2025. KFF estimates the expiration more than doubled the average net premium for subsidized enrollees — from about $888 in 2025 to roughly $1,904 in 2026, a 114% increase — and that the average Marketplace deductible grew by about $1,000 per person as enrollees shifted to cheaper, higher-deductible plans.
The mistake is assuming last year’s subsidy still applies and auto-renewing into a plan whose net cost has silently spiked. If your income sits just above 400% of the federal poverty level, you may have lost subsidy eligibility entirely — the group KFF found dropped coverage most sharply. Re-run your numbers on your state exchange, and if you’ve recently left a job, weigh the trade-offs in our comparison of COBRA versus marketplace coverage after job loss. Confirm your current ACA marketplace subsidy eligibility and savings before you commit, since the calculation changed under your feet.
What Most People Get Wrong
Beyond the headline errors, a handful of avoidable missteps recur every enrollment season. Each pairs a specific mistake with its consequence and the correct action.
Ignoring the drug formulary. Enrollees pick a plan on premium alone, then discover their maintenance medication moved to a non-preferred tier — turning a $30 copay into a $200 one. Correct action: check each plan’s formulary for your exact prescriptions before choosing, especially if you manage a plan selection with a chronic condition.
Assuming your doctor is in-network. Networks change annually. Staying with a plan whose name is unchanged does not guarantee your physician or hospital remains covered, and the gap can be brutal — see the real costs of going out of network. Correct action: verify every regular provider in the plan’s current directory during open enrollment.
Missing the enrollment deadline. Miss it and you generally wait until next year absent a qualifying life event. Correct action: calendar your employer’s window and the Marketplace period, which opened November 1, 2025, the moment it’s announced.
Overlooking prior-authorization rules. A covered service can still be denied if you skip pre-approval. Correct action: learn how prior authorization works and how to respond to a denial before you need an expensive procedure.
Who Should Spend the Most Time on Open Enrollment?
Not every enrollee faces the same stakes. The effort should scale with how much your circumstances changed and how much you spend on care.
If you had a baby, got married or divorced, changed jobs, or developed a new health condition this year, your prior plan choice is almost certainly no longer optimal — you should compare every option line by line. The self-employed and gig workers face the highest stakes of all in 2026, because the subsidy expiration hit them hardest; the coverage menu in our guide to health coverage options for the self-employed is worth a full read. Early retirees bridging the gap to Medicare should study coverage options for early retirees under 65, where a single wrong plan choice can cost thousands.
If your income or family situation shifted downward, check whether you now qualify for state Medicaid expansion eligibility and coverage before paying for a Marketplace plan you don’t need. For a stable single filer with steady income, no life changes, and minimal claims, a fifteen-minute total-cost check is usually enough — but “usually enough” still means opening the comparison tool, not skipping it.
Frequently Asked Questions
How much can I contribute to an FSA and HSA in 2026?
For 2026, the health FSA limit is $3,400 with a $680 carryover if your employer allows it (IRS Revenue Procedure 2025-32). The HSA limit is $4,400 for self-only and $8,750 for family coverage, plus a $1,000 catch-up at 55 or older (IRS Revenue Procedure 2025-19). You generally cannot contribute to a standard health FSA and an HSA simultaneously.
Did ACA subsidies really change for 2026?
Yes. The enhanced premium tax credits expired December 31, 2025. KFF estimates this more than doubled the average net premium for subsidized Marketplace enrollees, from roughly $888 in 2025 to about $1,904 in 2026 — a 114% increase. Enrollees just above 400% of the federal poverty level were affected most, so re-check your eligibility rather than assuming last year’s subsidy carries over.
Is a high-deductible plan always the cheaper choice?
No. An HDHP with an HSA usually wins for healthy, low-utilization enrollees because of the premium savings and triple-tax HSA advantage. But in a year with a major procedure, the low-deductible plan’s tighter cost-sharing can cost less overall. The 2026 HDHP out-of-pocket maximum is $8,500 self-only and $17,000 family (IRS), so model your expected spending against both ceilings before deciding.
How We Researched This Article
The federal contribution and cost-sharing figures in this article were drawn directly from primary IRS guidance. The 2026 health FSA limit ($3,400) and $680 carryover come from IRS published guidance and Revenue Procedure 2025-32. The 2026 HSA contribution limits ($4,400 self-only, $8,750 family), HDHP minimum deductibles ($1,700 / $3,400), and out-of-pocket maximums ($8,500 / $17,000) come from IRS Revenue Procedure 2025-19 as documented in Thomson Reuters’ regulatory summary.
Employer-market benchmarks — the $26,993 average family premium, $9,325 average single premium, $6,850 and $1,440 average worker contributions, and $1,886 average single deductible — are measured survey results from the KFF 2025 Employer Health Benefits Survey, which interviewed 1,862 firms. The ACA subsidy analysis, including the estimated jump from $888 to $1,904 in average subsidized net premiums and the roughly $1,000 rise in average Marketplace deductible, draws on KFF’s 2026 Marketplace enrollment analysis, which synthesizes CMS and state-based Marketplace data.
The break-even and forfeiture scenarios are modeled illustrations using stated assumptions, not measured outcomes; individual results vary with income, tax bracket, plan design, and actual utilization. Marginal tax examples assume a 22% federal rate and exclude state and FICA effects. Where enrollment rules or subsidy status may shift after publication, we noted the enacting authority so readers can verify current figures. This research was last conducted in July 2026. All figures were verified against named primary sources before publication.