What is prior authorization and why does it cause claim denials?

Prior authorization is pre-approval from an insurance company before a medical service, procedure, or prescription can be provided and covered. The insurer confirms that the requested care is medically necessary and falls within the patient’s plan benefits before committing to pay for it.

Common services requiring prior authorization include imaging studies like MRIs and CT scans, surgical procedures, specialist referrals, certain medications, durable medical equipment, and some diagnostic tests. Each insurance company maintains its own list of services requiring PA, and these lists change frequently.

Prior authorization causes claim denials in several predictable ways.

The most straightforward denial happens when a practice performs a service that required PA without ever requesting it. The claim comes back denied with a note that prior authorization was required. Some insurers allow retroactive authorization within a specific window, but many don’t.

PA approvals have expiration dates, typically 30 to 90 days depending on the insurer and service. If the patient’s procedure gets delayed and the authorization expires before the service is performed, the claim will deny. Practices need to track these dates and request extensions when appointments get rescheduled.

Authorization for one CPT code doesn’t cover a different code. If you obtain authorization for one procedure but end up billing something different, the claim denies. This happens when the actual procedure differs from what was initially planned, or when coding doesn’t match exactly what was approved.

Patient coverage changes cause problems too. A PA obtained from one insurance company is worthless if the patient switched plans before the service date. This is why verifying active coverage before every visit matters, not just when the patient first schedules.

PA requests require supporting documentation demonstrating medical necessity. If the initial request lacks sufficient clinical information, the insurer denies the PA, and any subsequent claim will also deny. Vague clinical notes are one of the most common reasons authorization requests get rejected.

Some practices proceed with services while PA requests are still pending, assuming approval will come through. If the PA is denied or takes longer than expected, the claim has no valid authorization to support it.

Prevention starts with knowing which services require PA for each insurance carrier your practice accepts. Build prior authorization verification into your scheduling workflow so nothing slips through. Track authorization expiration dates and flag any appointments approaching those deadlines.

When services change or expand during a patient visit, communicate immediately with your medical billing team so they can obtain additional authorization if needed. Document medical necessity thoroughly in every PA request because insufficient documentation leads to preventable denials.

For medical practices struggling with authorization-related denials, the problem is usually workflow rather than staff competence. Prior authorization isn’t just administrative paperwork. It directly determines whether your practice gets paid for the care you provide.