Prior authorization is a requirement from a health plan that a provider get approval before delivering a specific service, medication, or procedure. It confirms the plan considers the care medically necessary and agrees to cover it. Without that approval on file, the plan can deny the claim even when the care was clinically appropriate.
KEY TAKEAWAY
Prior authorization is the plan saying yes before the service happens. Skip it, and a perfectly valid claim can still be denied.
How Prior Authorization Works
The process runs before the visit or procedure, not after. The provider or their billing staff identifies that a service requires authorization, submits a request to the payer with supporting clinical documentation, and waits for a decision. The payer reviews the request against its medical-necessity criteria and either approves it, denies it, or asks for more information. Once approved, the plan issues an authorization number that has to be attached to the claim when it is billed. If the service is delivered before approval comes back, the practice is taking on the risk that the claim will not be paid.
Why Payers Require It
Payers use prior authorization as a cost-control and utilization tool. It lets them confirm, before spending, that a service meets their coverage rules, that a lower-cost alternative was considered where relevant, and that the care is not duplicative. For providers it is one of the most time-consuming parts of the revenue cycle, which is exactly why the requirement is being reformed.
Which Services Typically Require Prior Authorization
Requirements vary by payer and plan, but authorization is commonly required for advanced imaging, many surgical procedures, certain specialty and high-cost medications, durable medical equipment, and some diagnostic testing. Routine office visits usually do not require it. The only reliable way to know is to check the specific patient's plan during eligibility verification, since two patients with the same insurer can have different rules.
INSIGHT
Whether a service needs prior authorization often depends on which plan the visit is billed to. Authorization is a medical-plan concept, so the payer-routing decision at intake determines the entire authorization path.
How Long Does Prior Authorization Take?
Timing depends on the payer and whether the request is urgent. Under the CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F), impacted payers, including Medicare Advantage, Medicaid and CHIP managed care, and Qualified Health Plans on the federal exchange, must decide expedited requests within 72 hours and standard requests within 7 calendar days, with the decision-timeframe requirement taking effect in 2026. Commercial plans outside that scope still set their own timelines, which can range from same-day to a couple of weeks.
Prior Authorization and Claim Denials
Missing or invalid prior authorization is one of the most common and most preventable denial reasons. Because the requirement is known before the service, a no-auth denial is almost always avoidable with the right front-end process. The costly part is not the fix, it is that the care has already been delivered by the time the denial arrives, so the practice is now appealing or absorbing a loss it could have prevented at intake. This is why authorization belongs to the front desk and the eligibility check, not to the billing team after the fact.
Prior Authorization in Optometry and Eye Care
Eye care sits across two coverage systems, and that shapes when authorization applies. Routine vision-plan exams generally follow a different approval model, while medically necessary eye care, certain imaging, specialty procedures, and drugs like anti-VEGF injections, routes to the patient's medical plan where prior authorization rules do apply. That makes the medical versus vision routing decision the first thing that determines whether authorization is even needed. Confirming authorization requirements during insurance benefit verification, and again when coordinating primary and secondary plans, is what keeps these from turning into denials. For the full picture of how the front end drives reimbursement, see the optometry billing guide, and note that most optometry billing software can track authorization status alongside the claim.
What Is Changing in 2026
Prior authorization is in the middle of a reform cycle. Beyond the CMS decision-timeframe rule above, a group of major insurers pledged in June 2025 to reduce the volume of services requiring authorization, including common procedures like cataract surgery, to honor existing authorizations during coverage transitions, and to move toward real-time, standardized electronic authorization by 2027. The direction is fewer requirements and faster answers, but until those changes fully land, prior authorization remains a front-end task practices have to manage deliberately.
KEY TAKEAWAY
The rules are loosening, but not gone. Catching authorization requirements at check-in is still what separates a paid claim from a preventable denial.
Frequently Asked Questions
Is prior authorization the same as a referral?
No. A referral is a primary care provider directing a patient to a specialist. Prior authorization is a health plan approving a specific service before it is delivered. A visit can require one, both, or neither.
What happens if you skip prior authorization?
The claim is likely to be denied, and depending on the payer contract the practice may not be able to bill the patient for the difference. Some payers allow a retroactive authorization in limited circumstances, but it is not guaranteed.
Does prior authorization guarantee payment?
No. Authorization confirms medical necessity, but payment still depends on the patient's eligibility, active coverage, correct coding, and timely filing. An authorized service can still be denied for a different reason.
Do vision plans require prior authorization?
Generally vision plans use a different eligibility and authorization model than medical plans. Whether authorization applies usually comes down to whether the visit is billed to the medical plan or the vision plan, which is decided at intake.