Prior authorization requires a provider to obtain the insurer's approval before delivering certain care. It works as a cost and utilisation control placed ahead of the service rather than after it.
Review before treatment rather than after
An insurer can refuse payment for care it considers unnecessary, but doing so after treatment creates a bill nobody expected and a dispute in which the money has already been spent.
Moving the decision earlier lets the insurer apply its coverage criteria while alternatives are still open to the patient and the clinician, which is the argument the industry makes for the practice.
The requirement is applied selectively rather than universally, typically to expensive imaging, specialty medication, elective surgery and extended inpatient stays, where the spending at issue is large enough to justify the administrative cost of review.
Criteria are written rules rather than case-by-case judgement
Insurers maintain clinical policies describing what must be documented for a service to be approved, often including treatments that must be tried first.
Reviewers check submitted documentation against those written criteria. A request usually fails because a required element is missing, not because the care was judged wrong.
That is why resubmission with additional clinical notes frequently succeeds where the original request did not.
Step therapy is the same idea applied to medication
Step therapy requires a lower-cost drug to be tried before a more expensive one is covered.
Exceptions generally exist where the earlier drug has already failed or is contraindicated, but the exception must be documented and requested rather than assumed.
The mechanism is built around a typical patient, so the exception process is where atypical cases are meant to be resolved.
Approval is not a guarantee of payment
An authorization confirms medical necessity under the plan's written criteria. It does not confirm that the member was eligible on the date of service, that the provider was in network, or that a benefit limit had not already been exhausted.
Claims can still be denied afterwards on any of those separate grounds, and an approval number offers no protection against them.
Reading what an approval letter actually states, including its expiry date and the specific codes it covers, avoids assuming more coverage than it grants.
Denials have a defined appeal path
Plans provide internal appeals and, in many jurisdictions, an external review by an independent body. Timelines are short and are stated in the denial notice itself.
Expedited review exists where delay would threaten health, and a treating clinician can usually request it directly.
Rules on appeal rights differ by jurisdiction and change over time, so the notice remains the reliable source for any specific case.