While the Patient Protection and Affordable Care Act (ACA) allows parents to add their adult children (up to age 26) to their health plans, the IRS has not changed its definition of a dependent for HSAs.
If account holders can't claim an adult child as a dependent on their tax return, then they can't spend HSA dollars on services provided to that child.
Has the same principal place of residence as the covered individual for more than one-half of the taxable year
Has not provided more than one-half of his or her own support during the taxable year
Is not yet 19 (or, if a student, not yet 24) at the end of the tax year or is permanently and totally disabled