How it works
For Medicare, claims must be filed within 12 months of the date of service, with limited exceptions such as administrative error or retroactive entitlement. Medicaid programs and commercial plans set their own limits by state rule or contract, and these are often much shorter. Corrected claims and appeals have their own deadlines.
Why it matters
Claims denied for timely filing (CO 29) can usually only be recovered with proof that the claim was submitted on time — a clearinghouse acceptance report or an earlier remittance. Without proof, the amount is normally written off and cannot be billed to the patient.
Example
A claim was rejected by the clearinghouse and never corrected. Months later it is resubmitted and denied for timely filing; the rejection does not count as proof of filing because the claim never reached the payer. Working rejections daily prevents this. See A/R management.