Medical Billing and Denial Codes

CO 151 Denial Code: Test Frequency and Claim Review

CO 151 means the insurer questions the number or frequency of services. See what labs should check before correcting a claim or appealing the adjustment.

N823 Remark Code: Why a Modifier Needs Correction

N823 flags an incomplete or invalid procedure modifier. Check what the insurer received, confirm the billing rules, and identify the right correction

CO 50 Denial Code: Meaning and Checks for Lab Claims

Discover what the CO 50 denial code means, why insurers question medical necessity, and what labs should check before correcting or appealing a claim.

N822 Remark Code: Meaning and Missing Modifier Checks

Find out what the N822 remark code (RARC) means, why it appears on laboratory claims, and what to check when a required procedure modifier is missing.

Modifier 91: Meaning and Use in Laboratory Billing

Find out when modifier 91 applies to repeat laboratory tests, when it should not be used, and what records support its use on medical claims.

CO 97 Denial Code: Meaning and Checks for Lab Claims

Find out what the CO 97 denial code means, when insurers return it, and how laboratories can check, resolve, and prevent related claim errors.