What is prior authorization?
Prior authorization is the payer's approval, before a service, that it will cover it. Without one, a service that needs it is denied, usually as CO-197.
Prior authorization request
- Payer
- Example Health Plan
- Service
- 72148 MRI lumbar spine
- Diagnosis
- M54.16 Radiculopathy, lumbar
- Requested
- 02/01 to 02/28/2026
| Payer question | Answer | From the record |
|---|---|---|
| Six weeks of conservative care? | Yes | PT notes, Nov 2 to Dec 18 |
| Neurological deficit on exam? | Yes | Exam note, Jan 12 |
| Prior imaging of the area? | X-ray only | Radiology report, Nov 1 |
- Every answer is tied to a document, so a reviewer can check it, and the same evidence supports an appeal if the payer denies.
Payers require prior authorization for services they want to review before paying: advanced imaging, many surgeries, specialty drugs, durable medical equipment, therapy beyond a set number of visits, and more. The lists differ by payer and plan, and they change.
How a request works
- Check whether it’s required for this payer, plan, code and place of service.
- Gather the clinical evidence the payer’s policy asks for.
- Submit through the payer’s portal, a utilization management vendor, a 278 or fax.
- Answer pends, when the payer asks for more information.
- Record the decision: the authorization number, approved codes, units and dates, which must all match the claim later.
Where it goes wrong
Missing authorizations lead to CO-197. Authorizations that don’t match the claim lead to CO-198 and N54. Expired authorizations and used-up units catch recurring services by surprise.
What’s changing
Since 2026, CMS requires Medicare Advantage, Medicaid, CHIP and marketplace plans to decide standard requests within seven calendar days and expedited ones within 72 hours, and to give a specific reason for every denial.
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