What is prior authorization?

Prior authorization (also called pre-authorization or pre-certification) is a health plan's decision, made before a service is delivered, about whether the service meets its criteria for coverage. The practice asks, the payer reviews, and treatment usually waits for the answer. This guide explains the moving parts in plain terms.

Updated October 18, 2026 · Markdown version

The short definition

A payer (an insurer or a plan administrator) can require that certain services be approved before they happen. For those services the practice submits a request describing the patient, the planned service, the diagnosis and the clinical reasons the service is needed. The payer reviews it against its own medical-necessity criteria and answers: approved, partly approved, denied, or a request for more information.

Who does what

Roles in a prior authorization request
Who	What they do
The practice	Decides a service is needed, gathers clinical documentation, writes and submits the request, tracks it, and appeals if it is denied.
The payer	Sets the rules for which services need approval, reviews the request against its criteria, and issues a decision with a reason if it is not a full approval.
The patient	Is affected by delays and denials, and usually has appeal rights of their own. Practices often keep the patient informed while a request is pending.

Why payers require it

To check that a service meets the plan's clinical criteria before paying for it.
To steer toward a less costly alternative when the plan considers one equivalent.
To confirm the patient is eligible and the service is covered under their plan.

Why it is expensive for small practices

Each request is a small writing project: the clinical story has to be turned into the language a reviewer expects, the right codes have to match the narrative, and the supporting documents have to be attached. Requirements vary by payer, so experience with one payer does not transfer cleanly to the next. A missing document or a vague justification is a common reason for a request to come back, and that costs another round.

An approval is not a guarantee of payment

Authorization generally means the service was found to meet medical-necessity criteria at the time of review. Payment can still depend on the patient's eligibility on the date of service, benefit limits and the service being delivered as described. Read the approval for its scope: the codes, dates and number of visits or units it covers.