A payer is the organization that pays for your care — an insurance company, a Medicare Advantage plan, a state Medicaid program. You mostly meet payers through cards in your wallet and letters that begin "This is not a bill." Behind those letters, a payer is fundamentally a data operation.

Here's the data a payer holds about you, and what each piece does:

Enrollment and coverage. Who you are, which plan you're on, what it covers, your deductibles and copays. In FHIR terms this becomes Patient and Coverage — the building blocks nearly every other transaction points back to.

Claims. Every visit, prescription, and procedure that anyone billed to your plan. Claims are the payer's memory of your care — often more complete than any single doctor's chart, because every provider you've seen bills the same payer. That's why claims data matters for your history, and why the law now requires payers to share it with apps you authorize.

Prior authorization requests. For certain services, your doctor must ask the payer for approval before treating you. That request bundles clinical evidence — diagnoses, procedures, notes — and the payer's answer (approved, denied, or "we need more") gates your care. This is the paperwork the Da Vinci PAS standard turns into structured, machine-readable exchange.

Utilization and care management. Payers analyze the above to flag gaps in care, manage chronic conditions, and — less charitably — to decide what to scrutinize. The same data drives both.

What the law changed: payers in federal programs must now expose this data through standard FHIR APIs — to you (Patient Access API, including your prior-auth status), to your providers (Provider Access API), and to your next payer when you switch plans (Payer-to-Payer API). The prior-auth process itself gets an API with a deadline of January 1, 2027 for Medicare Advantage and Medicaid/CHIP plans.

The honest caveat: a payer sharing your data through an API you authorize is the intent of these rules; the quality and completeness of what arrives varies by payer. And nothing on this site touches real payer data — the Lab runs entirely on synthetic examples so builders can test the plumbing safely.