# Prior authorization guides

Source: https://priorauth.getgenko.com/guides

- [What is prior authorization?](https://priorauth.getgenko.com/guides/what-is-prior-authorization): Prior authorization is a payer's approval, requested before a service, that it meets medical-necessity criteria. Who does what, and why it takes time.
- [What goes in a prior authorization packet](https://priorauth.getgenko.com/guides/prior-authorization-packet-checklist): A checklist of what a prior authorization request usually contains: identifiers, codes, clinical justification, supporting documents and the request letter.
- [Appealing a prior authorization denial](https://priorauth.getgenko.com/guides/appealing-a-prior-authorization-denial): What to do when a payer denies a prior authorization request: read the reason, check the deadline, add what was missing and appeal in writing.