Denial code · CARC 29
CARC 29 (CO-29): timely filing denials in behavioral health
What CO-29 means, the filing limits in Medicare and Medicaid, why behavioral-health programs hit them, and how proof of timely filing works.
By the ClaimParrot editorial team · Who we are · Reviewed · 4 min read · 6 cited sources
Quick answer
CARC 29 means the payer received the claim after its filing deadline and will not pay it. Medicare allows 12 months from the date of service, Medicaid programs must require claims within 12 months, and commercial limits are set by contract and can be shorter. The fix is proof that a valid claim reached the payer in time, or a recognized exception.
| Item | Detail |
|---|---|
| Code | CARC 29 · Active on the X12 list; checked October 14, 2026 |
| Plain meaning | The payer received the claim after its filing window closed, so it will not pay unless you prove timely submission or an exception applies. |
| Group codes seen | CO (contractual obligation) |
| Common remark codes | N211, N1, N921 |
| Where it shows up in BH | Outpatient therapy, Residential mental health, Intensive outpatient (IOP), Psychiatry and medication management |
| Usual next step | Reconsideration with proof of timely filing |
| Related codes | CARC 16, CARC 185, CARC 170 |
What does CARC 29 mean?
CARC 29 is a procedural denial: the payer is not judging the care, only the date a valid claim arrived. What counts is when the payer received a complete claim, not when you sent one or when a rejected version went out. Medicare, for example, does not treat incomplete or invalid submissions as filed.
What does CO-29 mean for who pays?
CO-29 is the normal form, and it is a write-off unless you prove timely filing. Medicare goes further: when the provider caused the late filing, the patient can be charged only the deductible and coinsurance that would have applied had Medicare paid the claim.
| Group + reason | What it signals | Who usually carries the balance |
|---|---|---|
| CO-29 | Payer received the claim after the deadline | Provider; do not bill the patient for it |
Which remark codes come with CARC 29?
Timely filing denials often carry few remark codes, but these change what you can do next.
| Remark code | What it adds | What to check |
|---|---|---|
| N211 | The payer says this decision cannot be appealed. | Whether the payer allows any review of the filing decision |
| N1 | You may appeal in writing within the time limits in your contract, plan or the payer's instructions. | The review route and window your contract gives you |
| N921 | The window to ask for a reconsideration or appeal has closed (added to the RARC list in March 2026). | Different problem: the appeal window closed, not the filing window |
Where does CARC 29 show up in behavioral health?
Behavioral-health programs miss filing windows for predictable reasons: claims held while a new clinician is credentialed, long stays billed only at discharge, secondary claims waiting on a primary payer, and rejected claims nobody worked. Each has a different fix, so find the cause before asking for a review.
| Care setting | Typical trigger | Check first |
|---|---|---|
| Outpatient therapy | Sessions held for months while a new clinician's enrollment was pending | Enrollment effective date and any retroactive billing allowance |
| Residential mental health | Long stay billed only at discharge | Interim billing rules; Medicare counts institutional span claims from the through date |
| Intensive outpatient (IOP) | Clearinghouse rejection never worked, so no valid claim reached the payer | Rejection reports and the first accepted submission |
| Psychiatry and medication management | Secondary claim sent long after the primary remittance | Primary remittance date and the secondary payer's rule |
Corrected claim, reconsideration or appeal: which fits CARC 29?
Do not argue the care. Ask for a reconsideration that proves a valid claim reached the payer in time, or that a recognized exception applies. In Medicare a late-filing decision is not an initial determination and cannot be appealed; only exceptions such as administrative error or retroactive entitlement extend the deadline.
- 01Find the first accepted submission: the payer's acceptance record or claim number, not just your send log.
- 02Check exceptions: payer error, retroactive Medicare or Medicaid eligibility, and contract terms for corrected claims.
- 03Send the proof through the payer's reconsideration or timely-filing review, and fix the process that let the claim age.
What evidence resolves a CARC 29?
Proof of timely filing is documentary and date-stamped. The payer wants evidence that it, not only your clearinghouse, received a valid claim inside the window. Your own send log is weaker than the payer's acceptance record, so lead with the payer's evidence and add the rest.
- Payer or clearinghouse acceptance reports with dates
- The payer claim number from the first accepted submission
- Rejection reports showing when earlier attempts failed and why
- Eligibility responses showing retroactive coverage
- Correspondence showing a payer error delayed filing
How do Medicare, Medicaid and commercial plans differ on CARC 29?
Deadlines differ sharply. Medicare sets one year from the date of service with narrow exceptions; Medicaid programs must require claims within 12 months; commercial plans and managed care contracts set their own limits, which can be much shorter. Check the contract, not a general rule.
| Program | What differs |
|---|---|
| Medicare (Original) | 12 months from the date of service (the through date for institutional span claims). Late-filing decisions are not appealable; exceptions cover administrative error and retroactive entitlement or disenrollment. |
| Medicaid | States must require claims within 12 months of the date of service; managed care contracts may set other limits. |
| Commercial and ERISA plans | Set by the provider contract and payer manual; corrected claims can have their own window. |
CO-29 on claims held during credentialing
A fictional practice held a new psychologist's claims for one commercial plan until her credentialing finished. Seven months later the claims went out and came back CO-29; the contract allowed 90 days from the date of service.
With no earlier submission to prove, the practice asked whether the plan's own credentialing delay counted as an exception, and changed its process to track each payer's filing window from the date of service.
Names, dates, payers and amounts are invented for illustration.
What a ClaimParrot packet does here
- When CARC 29 needs an appeal rather than a corrected claim, an appeal packet answers the payer's stated reason.
- A person checks every packet: $29, or $99 for level of care, and the first is free (pricing).
- No remittances, records or PHI are sent: just the reason and a de-identified summary (Trust & security).
Every draft is reviewed and approved by your team. ClaimParrot does not make medical-necessity determinations or give legal advice.
Frequently asked questions
Can a Medicare timely filing denial be appealed?
No. Medicare treats a late-filing decision as outside the appeal process. You can only show the claim was in fact timely or that an exception applies, such as an error by Medicare or its contractor.
Does a rejected claim count as filed on time?
Usually not. A claim the payer rejected as incomplete or invalid generally does not count as filed. Keep rejection and acceptance reports, and work rejections quickly so a valid claim arrives inside the window.
Can we bill the patient after a CO-29?
No. CO puts the amount on the provider. Medicare also limits the patient's charge to the deductible and coinsurance when the provider caused the late filing.
How is CARC 29 different from remark code N921?
CARC 29 means the claim itself arrived late. N921, added in 2026, means the window to ask for a reconsideration or appeal has closed. They are different deadlines with different fixes.
Primary sources and references
- Claim Adjustment Reason Codes (CARC) code list · X12 · checked
- Remittance Advice Remark Codes (RARC) code list · X12 · checked
- 42 CFR 424.44: time limits for filing Medicare claims · eCFR · checked
- Medicare Claims Processing Manual, Chapter 1, §70 (timely filing) and §80.3 (incomplete or invalid claims) · CMS · checked
- 42 CFR 405.926: Medicare actions that are not initial determinations · eCFR · checked
- 42 CFR 447.45: Medicaid timely claims payment and the 12-month filing rule · eCFR · checked
General information, not legal or medical advice. Payer rules change; confirm deadlines and requirements in the notice and the plan documents. Read our editorial policy.
Decode the next line on the remittance.
Type a group and reason code such as CO-197 or PR-96, or a remark code such as N386. The lookup runs in your browser and needs no patient details.