First of all, you can use HSA funds to pay for expenses for yourself, a spouse, a dependent, or a person who could be a dependent if the only thing that disqualifies them is having income more than $4200, or the fact that they filed a joint return with a spouse.
In the case of a child who does not qualify as a dependent because they are 19 or older and not a full time student, or age 23 or older, you can still claim them as a dependent if you provided more than half their total financial support AND their income is less than $4200. Since the income test does not apply to spending HSA funds on their care, the only real test (most of the time) is did you pay more than half their support? Support includes a share of the rental value of your home if they live with you, including a share of food, utilities, property taxes and repairs; as well as direct financial support including tuition payments, tuition you pay for with loans in your name, money for clothing, travel and medical expenses, and of course, part of the medical insurance premiums.
Are you still convinced the child does not qualify for you to pay their medical expenses from the HSA?
