What is a claim denial?
A claim denial occurs when an insurance payer refuses payment for a submitted claim - commonly because of a missing authorization, a coding error, an eligibility issue, or incomplete documentation.
A denial is not the same as a rejection: a rejected claim never made it into the payer's system, usually because of a formatting or data error, while a denied claim was processed and refused. Either way, no payment is issued until the problem is corrected.
Common causes in ABA include services delivered outside an active authorization or beyond approved units, an incorrect code or modifier combination, a client whose coverage has lapsed, and session notes that don't support what was billed.
Most denials can be corrected and resubmitted or appealed, but each one costs staff time and delays payment. Practices reduce them by verifying eligibility up front, tracking authorizations, and building claims from documentation that is already complete.
Payers explain denials through standardized reason and remark codes on the remittance advice. Reading those codes rather than guessing is what separates a corrected claim from a resubmission that gets denied again for the same cause. They also distinguish a denial that can simply be fixed and resent from one that requires a formal appeal with supporting documentation.
Appeals are time-limited, and the deadline runs from the payer's decision rather than from when the practice noticed. Missing it generally forfeits the claim regardless of merit, so denials are usually worked on a schedule instead of when someone gets to them. Appeals that succeed tend to be the ones that attach the specific evidence the denial reason asks for - the authorization, the session note, the credentialing confirmation - rather than a general letter of disagreement.
The more useful way to treat denials is as a diagnostic. One denied claim is an administrative task; the same reason code appearing across many claims points at something upstream - an expired authorization nobody was tracking, a clinician whose enrollment lapsed, a modifier applied under the wrong payer's rules. Practices that categorize denials by cause end up fixing the process, while practices that only rework them individually keep paying for the same error.