An eligible expense is a purchase a funding program counts as allowable — curriculum, certain materials, tutoring, and so on. The catch is that each program defines 'eligible' differently, and the line can be fuzzy, so what clears in one state may not in another. That's why keeping the receipt and a note on the purpose matters: if a purchase is ever questioned, the record is your answer. About Time's ESA Wallet tracks and organizes those receipts and notes — it doesn't decide eligibility or file anything, which only your program can do.