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Short answer: A health FSA pays only against proof. IRS Publication 969 says you must give the plan a written statement from an independent third party that the expense was incurred and its amount, plus your own written statement that no other health plan has paid or reimbursed it. In practice a supplier receipt or invoice showing the item, the date and the amount is the usual third-party document. A plan administrator can ask for more.
General information about how claims are substantiated, drawn from IRS texts. It is not tax, legal or medical advice; your plan document and administrator decide what your plan accepts.
Definition and scope
“Substantiation” is the step in which a health flexible spending arrangement (FSA) checks that a claimed expense is a real, eligible medical expense incurred during the period of coverage. This page covers the paperwork side only. For what counts as an eligible item, see the FSA eligible items list; for how FSA paperwork differs from HSA paperwork, see the letter of medical necessity guide.
What a health FSA claim must show (IRS Publication 969)
Publication 969 sets out the legal skeleton in three statements:
- Independent third-party statement. The plan must receive a written statement from an independent third party stating that the medical expense has been incurred and the amount of the expense.
- No other coverage. You must also provide a written statement that the expense has not been paid or reimbursed under any other health plan coverage.
- No advances. The FSA cannot make advance reimbursements of future or projected expenses, and the expense must be incurred during the period of coverage.
A supplier’s receipt or invoice is a natural fit for the first statement, because the seller is independent of you and the document states what was sold and for how much. The second statement is yours to make, not the supplier’s.
Paying by FSA card versus paying out of pocket
Revenue Ruling 2003-43 illustrates how an employer may run substantiation for employer-provided debit, credit or stored value cards. Publication 969 says that if card use meets certain substantiation methods, you may not have to provide additional information to the health FSA.
| Situation | What the IRS source says |
|---|---|
| Card charge that matches a copayment, a recurring expense, or is confirmed in real time | In the ruling’s example, these are not treated as conditional; all other card charges are. Real-time substantiation by the provider confirms the type of care, date and amount without further review. |
| Any other card charge | Treated as conditional pending confirmation of the charge. The employer may require additional third-party information, such as merchant or service provider receipts, describing (1) the service or product, (2) the date of the service or sale and (3) the amount. |
| Paid out of pocket, no card | In the ruling’s example, the employer accepts an Explanation of Benefits (EOB) from a health insurer, or a receipt from a merchant or service provider showing that funds are owed for an eligible medical expense. |
| Estimate, quote or future purchase | Publication 969: no advance reimbursement of future or projected expenses. |
What a receipt or invoice should describe
The three elements the example employer in Revenue Ruling 2003-43 asks for give a short checklist to ask a supplier for before you pay:
- The product or service described in words a reviewer can match to an eligible expense, not only a product code.
- The date of the sale or service, which must fall within your coverage period.
- The amount.
These three are what the ruling’s example employer requires, not a minimum the IRS sets for every plan. Your plan administrator sets its own document list, so follow your plan for what it accepts.
Why estimates and quotes do not count
A quote or pro forma estimate states what an expense may cost, not that it has been incurred. Publication 969 requires a statement that the expense has been incurred and the amount, and bars advance reimbursement of projected expenses. A quote can support planning, but it is not the document that substantiates a claim.
Where it matters for labs, clinics and supply orders
Individuals sometimes buy medical supplies for personal use and claim them against an FSA. The paperwork rule is the same whatever the product: the seller’s document needs to show what was bought, when and for how much. Where an employer or plan treats a charge as conditional, the kind of receipt request illustrated in Revenue Ruling 2003-43 may apply. For the related tax-deduction rules, see medical expenses you can deduct and HSA qualified medical expenses.
Common misunderstandings
- “Using the card means no paperwork.” Only if the charge is substantiated by an accepted method; other card charges are conditional until confirmed.
- “The plan can pay me in advance.” Publication 969 says it cannot reimburse future or projected expenses.
- “My own statement is enough.” Your statement covers the no-other-coverage point; the incurred-and-amount statement must come from an independent third party.
- “The IRS prescribes one receipt format.” The ruling’s example describes the content an employer asked for (product or service, date, amount), not a prescribed form.
FAQ
What must an FSA receipt include?
In the example in Revenue Ruling 2003-43, the employer asks that third-party documents such as merchant or service provider receipts describe the service or product, the date of the service or sale, and the amount. Your plan may require more.
Do I need a receipt if I paid with my FSA card?
Not always. Publication 969 says card use that meets certain substantiation methods may not require additional information, but conditional charges can trigger a receipt request.
Can I claim an expense before I pay for it?
No. Publication 969 says the FSA cannot make advance reimbursements of future or projected expenses.
Is a credit card slip enough?
The ruling’s example employer asks for these details on the third-party document (product or service, date, amount). Whether your plan accepts a given document type is set by your plan administrator.
Sources
- IRS, Publication 969, Health Savings Accounts and Other Tax-Favored Health Plans, health FSA distributions section; checked 2026-11-01.
- IRS, Revenue Ruling 2003-43 (2003-21 I.R.B. 935); checked 2026-11-01.
