The primary concern is not how you paid it initially, but whether the expense was an eligible HSA expense. An eligible expense will diagnose or treat an illness injury or condition that is for yourself, your spouse, or a current tax dependent at the time of the expense, and must have occurredafter the time you funded your HSA account. In other words, was it a qualified expense for an eligible person from an eligible account? If you can answer yes to all three, you should be able to use HSA funds to pay off that balance. For instance, if it was for a cosmetic dental procedure, like teeth whitening, it would not qualify.