MassMutual cites other data from Aite Group showing usage of HSAs is projected to outpace other financial accounts for health care such as health reimbursement arrangements (HRAs) and flexible spending accounts (FSAs) by 2021. Notably, while HRAs and FSAs require eligible expenses to be validated by a third party, the IRS does not require such validation for HSAs. However, it is required that consumers keep all of their medical receipts for eligible expenses in the event of a tax audit.