Pull 12 months of billed charges, not premiums. EOBs, Explanation of Benefits, the claims tab — allowed amount or billed, consistently. Premiums are the other column in the calculator. If you only remember “we didn’t hit the deductible,” write $800, not $0. New baby, new specialist, a surgery already scheduled: put it in the bad-year box before you fall in love with the HDHP.
Print the two SBCs side by side and run the IRS test. 2027 HDHP: deductible at least $1,750 self / $3,500 family, in-network OOP at most $8,700 / $17,400 (Rev. Proc. 2026-24). Copays that fire before the deductible on non-preventive care can spoil the HSA. The word “high deductible” on a benefits-fair slide is not a test. If either number fails, you do not have an HSA path. You have a cheaper-looking copay plan with a large deductible.
Confirm you can contribute at all. Covered by that HDHP, not enrolled in Medicare, not claimed as a dependent, no other disqualifying coverage (including a spouse’s general FSA that reimburses your medical). Last-month rule and partial-year proration are Pub. 969, not Slack folklore. Age 65 next year is a funding calendar, not a surprise.
General FSA vs HSA is binary. If the cafeteria plan only offers a general health FSA, electing it next to the HDHP is how HSA contributions become excess. Limited-purpose (dental / vision, or post-deductible medical) is the legal stack. Dependent-care FSA is a different Code section — $7,500 in 2026, spouse’s remaining unused capacity, not an HSA decision. Do not mix the three forms in your head.
Size a cash sleeve of about 1× the deductible in HYSA before you click elect. The invested HSA is not January ER money. If that sleeve would be a credit card, you wanted the copay plan. The emergency-fund guide is the other half of this election.
Run the calculator at light, typical, and bad. Typical from step 1. Light $500. Bad a hospitalization-shaped $12,000 or your actual OOP max as billed. If HDHP wins typical and light, and the bad year still fits the sleeve, elect HDHP. If only the tax slogan wins and the bad year does not fit, elect the copay plan and a sized FSA. Split decisions are allowed.
Employer HSA seed counts toward the cap. 2027 self-only $4,500, family $9,000, +$1,000 if 55+. A $1,000 seed plus a $4,500 election on self-only is $1,000 of excess, not a match to “max.” True-up, pro-rata if you mid-year, and the payroll source code (HSA vs medical FSA vs limited FSA) belong on a sticky note for HR.
Prefer payroll HSA over a 1040 contribution. Payroll usually skips FICA. A contribution by the filing deadline is an above-the-line deduction and does not unwind FICA already withheld. If cash is tight in November, elect a smaller payroll amount you will not reverse, then top up from a bonus later — still payroll if the plan allows after-tax-to-HSA. Reversing an FSA election after the plan year starts is the thing the document usually forbids.
FSA election is last year’s known plus $0 wishful. Braces, glasses, a scheduled procedure: in. “We might do a lot of PT”: out, or in the HDHP patient-share instead. 2026 salary reduction $3,400, carryover $680 or a 2.5-month grace — not both (Rev. Proc. 2025-32). 2027 FSA dollars were not published as of September 2026; copy the SPD. Unused FSA is a fee you paid yourself.
Open the receipt shoebox the week the plan year starts. PDFs, not a drawer. Qualified expenses after the HSA exists can be reimbursed years later. That is the compounding trick in the triple-tax primer. Paying the deductible from cash and leaving the HSA invested is the move only if the sleeve in step 5 exists. Investing the HSA in the plan’s 0.4% cash sweep is how people donate the triple-tax to the custodian.
Medicare year is a last-contribution year, not a spend-down. Contributions generally stop the month you are enrolled. Plan the last funded year the open enrollment before. Receipts stay. After 65, non-medical HSA withdrawals are ordinary income like a traditional IRA — usable, not magic. IRMAA is a MAGI problem; HSA payroll still helps MAGI while you are eligible. See the IRMAA playbook if you are inside two years of Part B.
Hard-stop list: electing a general FSA “just in case” on an HDHP, maxing the HSA on a 22% card, treating a copay clinic HDHP as eligible without the IRS test, skipping the 401(k) match to fill the HSA (match first — order of operations), and assuming the HSA is a checking account because the debit card came in the mail. If the calculator’s bad year does not fit next to rent, you wanted the other plan.
One-page decision
Cashable deductible + HDHP that actually passes Rev. Proc. 2026-24 + typical and light years that win: HDHP, payroll HSA to the cap minus the seed, limited-purpose FSA if it exists, receipts in a shoebox. Tight cash, scheduled medical, skinny premium gap, or a failing HDHP test: copay plan plus an FSA you can finish. Dependent-care FSA is a third form. Medicare is a calendar. Nobody is required to take the tax slogan.