The Affordable Care Act will require plans to allow adult dependents to stay on their parents plan for longer duration--until age 26. Tied to this requirement, the federal tax code was changed to allow pre-tax coverage for these individuals during this time.
While both of these rules apply to high deductible health plans (commonly called HDHPs), neither of these rules apply to Health Savings Accounts (HSAs). Since these accounts can run along side the HDHP plan, this creates two different eligibility rules for participants. For example, the adult child may get tax free medical under the major medical plan (HDHP), but they may not be eligible for tax free reimbursements under the account (HSA). Non-qualified reimbursements from an HSA are also subject to higher tax penalties under the Affordable Care Act and may be subject to state taxation.
If you need help understanding these rules or other HSA rules, please contact Kinney & Larson.