CO-197 Denial: Prior Authorization Missing or Not Obtained

Why it is so hard to fix after the service

Most payer contracts state that authorization must be obtained before the service, and most will not backdate one. Retroactive review is sometimes available for genuinely urgent care or for retroactive eligibility, and those are narrow exceptions with their own filing deadlines. Outside them, the practice is arguing for an exception rather than appealing a decision.

For a buy-and-bill biologic the exposure is worse than the professional fee, because the practice has already paid acquisition cost on a drug that has already been administered. A single missed authorization on a high-cost agent can exceed a month of professional collections.

The workflow that prevents it

• Authorization requirements checked at scheduling, against the specific plan rather than the payer name — requirements differ sharply between a payer's commercial, exchange and Medicare Advantage products.
• Benefit verification repeated close to the date of service, since plan changes and terminations are the second most common cause after the requirement simply being missed.
• Authorization numbers, approved units and valid date ranges stored where the biller sees them at claim build, not in a fax folder.
• Expiry tracked for treatment courses. A phototherapy authorization covering a fixed number of sessions across a fixed window will silently run out mid-course.
• A stop rule: high-cost drugs are not administered without confirmed authorization on file, with an explicit clinical override path so the decision is made by a person rather than by omission.

When you do have to appeal it

Where an authorization existed but the claim was denied anyway, this is usually a mismatch rather than an absence: the code billed differs from the code authorized, the units exceed those approved, the rendering provider differs from the one on the authorization, or the date falls outside the approved range. Those are corrected claims, not appeals, and they resolve quickly once the mismatch is identified.

Where no authorization existed, the argument has to be an exception — urgency, retroactive eligibility, or a documented payer representative's statement that none was required. That last one is why calls to payers need reference numbers and representative names recorded at the time, because it is the only evidence that argument ever has.