CO 146 Denial Code — Meaning, Causes, and Fixes (Medicaid 2025 Guide)
Introduction
When a Medicaid claim is denied with CO 146, it means one thing:
“Claim or service was submitted after the time limit for filing expired.”
This denial appears most often in Medicaid and Managed Care Organization (MCO) claims — not Medicare — and signals that the provider missed the timely filing window set by the payer or state Medicaid agency. While code CO 29 denial is the universal time-limit denial for Medicare, 146 CO denial is uniquely associated with Medicaid and MCO timely filing enforcement. In 2025, as states tighten their claim-processing systems and post-COVID filing extensions have expired, CO-146 denial is appearing more frequently than ever.
What Does CO 146 Denial Code Mean?
According to the official CO 146 denial code description, this denial occurs when the claim reaches the payer after the allowed filing window has closed. That means the payer rejects it simply because it was submitted too late. It is a Claim Adjustment Reason Code (CARC) used primarily in Medicaid and Managed Care Organization (MCO) billing. While the code may occasionally appear in commercial claims, it is most commonly associated with state Medicaid systems that enforce strict timely filing requirements (for example, 95 days in Texas, 90 days in New York, or 180 days in Illinois).
This reason code is often accompanied by a Remittance Remark Code (RARC) for further detail — for example:
- N39011: “Timely filing expired.”
- MA39: “Missing or incomplete information caused claim to exceed timely filing.”
Where does CO146 Denial Code Appear
- Medicaid Fee-for-Service (FFS): State systems automatically reject claims received after their internal filing limit.
- Medicaid Managed Care (MCO): MCOs like Molina, Aetna Better Health, Wellcare, and UnitedHealthcare Community Plan apply their own (usually shorter) limits, often 90–180 days.
- Crossover or Dual-Eligible Claims: Sometimes triggered when the Medicare claim crosses over to Medicaid after the window closes.
Why CO-146 Denial Code Matters in 2025
In 2025, nearly all states have reinstated standard timely filing rules that were temporarily relaxed during the COVID-19 emergency period. That means no more leniency — claims must strictly meet each payer’s published time-frame, or they will deny automatically under CO 146. Billing teams must now track these windows state by state and plan by plan, since even one missed day can turn a payable claim into a permanent denial.
| Aspect | CO 146 |
|---|---|
| Definition | Claim/service submitted after the time limit for filing claim/service expired. |
| Primary Use | Medicaid and Managed Care Organization (MCO) claims. |
| Regulation | Governed by 42 CFR §447.45(d) — states set their own limits. |
| Filing Limit | Fixed at 12 months from the date of service. |
| Proof Requirement | Must show timely submission (EDI 277CA, eligibility letter, or portal log). |
| Exceptions | State-defined (e.g., retroactive eligibility, provider enrollment delay). |
| Appeal or Reopening Rights | Through state Medicaid or MCO appeals |
| Common Remark Codes | N39011, MA39, CO 252. |
| Consequence of Missing Deadline | Often final, unless exception approved by state or MCO. |
When Does Denial Code CO 146 Appears?
Denial code 146 usually appears when a Medicaid or Managed Care Organization (MCO) claim is received after the allowable filing period. While it might sound like a simple timing error, in practice, several operational and technical factors cause this denial — many of which can be prevented with better tracking and documentation. Below are the most common scenarios that lead to CO 146 denials:
1. Filing After the State or MCO Deadline
The most direct cause: the claim was submitted after the payer’s filing window expired.
- Example: Texas Medicaid (TMHP) allows 95 days from the date of service. A claim submitted on the 100th day will automatically deny with CO 146.
- Even one-day delays count, as Medicaid measures timeliness by receipt date, not postmark.
2. Rejected (RTP) or Returned Claims Not Corrected in Time
If a claim was initially rejected for errors (like missing diagnosis codes or invalid member IDs) and wasn’t corrected within the filing period, it still counts as late.
- Example: Claim rejected on day 40, corrected on day 200 — even though you first submitted early, the resubmission exceeded the limit.
- Medicaid requires the processable claim to arrive within the timely filing window.
3. Missing Proof of Timely Submission
Sometimes the claim was submitted on time, but the provider can’t prove it.
- Clearinghouse logs, EDI reports, or 277CA acknowledgments weren’t saved or attached.
- The payer’s system didn’t register the claim receipt date.
- Without proof, Medicaid assumes the claim is late and issues CO 146.
4. Provider Enrollment or Revalidation Delays
A provider who isn’t fully enrolled in Medicaid during the date of service can’t bill — even if the claim is timely later.
- When enrollment is approved retroactively, claims often deny with CO 146 unless you attach the enrollment approval letter showing the effective date.
5. Claims Submitted to the Wrong Payer or MCO
Another frequent cause is sending the claim to the wrong plan or payer ID.
- Example: Patient switched from Aetna Better Health to Molina during the month.
- If you billed the wrong MCO first, by the time it’s corrected and rebilled, the new plan’s window may have expired — triggering CO 146.
CO 146 doesn’t always mean negligence — it often reflects process breakdowns between your billing system, clearinghouse, and payer. Still, Medicaid payers rarely grant flexibility without documented evidence, so timely filing proof (EDI reports, logs, acknowledgment numbers) is essential.
State Level Interpretation of CO 146 Denial in 2025
Denial code CO 146 is universal in meaning but not in application. Each state Medicaid program — and sometimes each Managed Care Organization (MCO) — interprets and enforces this denial based on its timely filing window and internal claim processing system. Here are real-world examples showing how CO 146 appears in different Medicaid programs in 2025:
1. Georgia Medicaid
- Filing limit: 6 months (180 days) from the date of service.
- Resubmission window: 12 months for retroactive eligibility.
- CO 146 use: Issued automatically when claims exceed 180 days without an approved exception.
- Notes: Appeals are not accepted for CO 146 unless the provider attaches retroactive eligibility documentation or proof of timely submission.
2. Illinois Medicaid (HFS)
- Filing limit: 180 days from DOS.
- Resubmission window: 180 days after denial.
- CO 146 use: Common for institutional providers submitting corrections beyond 180 days.
- Notes: HFS requires proof of timely original submission (EDI report or portal confirmation). Without it, late resubmissions are rejected with CO 146 again.
3. Pennsylvania Medicaid (DHS / MCOs)
- Filing limit: 180 days for both fee-for-service and most MCOs.
- CO 146 use: Frequent in MCO ERAs when providers submit to the wrong plan first.
- Notes: Providers must appeal directly with the MCO within 60–90 days of denial, including evidence that the claim was first filed timely.
4. Texas Medicaid (TMHP & MCOs)
- Filing limit: 95 days from the date of service.
- CO 146 use: Appears in both fee-for-service and managed Medicaid rejections.
- Notes: Texas uses a strict receipt-based deadline — even a claim sent on day 94 but received on day 96 is late. TMHP allows reopening only with an approved exception form (e.g., retroactive eligibility or system error).
5. New York Medicaid (eMedNY)
- Filing limit: 90 days from date of service.
- CO 146 use: One of the most common denials in the state.
- Notes: Providers must request an extension from the Department of Health (DOH) within the same quarter as the denial. Exception approvals require written justification and supporting documents such as eligibility proofs.
6. Florida Medicaid (AHCA / MCOs)
- Filing limit: 12 months (state FFS); 90–180 days for MCOs.
- CO 146 use: Typically tied to late MCO submissions or claims sent to incorrect payers.
- Notes: AHCA allows late claim certification using Form 2040 – Timely Filing Certification Statement if supported by evidence of retroactive coverage or administrative error.
| State | Typical Filing Limit | CO 146 Frequency | Appeal Options |
|---|---|---|---|
| Georgia | 180 days | High | Limited – exception proof required |
| Illinois | 180 days | Medium | Reopen with proof of timely original |
| Texas | 95 days | Very High | Reopen via TMHP with valid documentation |
| New York | 90 days | Very High | DOH extension request only |
| Florida | 90–365 days | Medium | AHCA Form 2040 certification allowed |
How to Fix CO 146 Denials (Step-by-Step Guide)
This section converts the problem into a process — it tells billing teams exactly what to do after receiving a CO 146 denial, how to verify eligibility for exception, and how to reopen claims under 2025 Medicaid rules.
How to Fix CO 146 Denials (Step-by-Step Guide)
When a Medicaid claim is denied with CO 146, it usually means the payer believes your claim was submitted after the allowed time window. The good news: some of these denials can be overturned — but only with solid documentation and a clear exception reason recognized by the state or MCO. Follow these steps carefully to correct or appeal a CO 146 denial in 2025:
Step 1: Confirm the Filing Deadline
Before doing anything, verify the timely filing limit for that claim’s payer:
- Check your state Medicaid provider manual or MCO contract.
- Remember that MCOs often have stricter limits (e.g., 90–180 days).
Example: Texas Medicaid allows 95 days; Aetna Better Health in the same state allows only 120 days.
If the claim truly missed the payer’s limit, you’ll need an exception to reopen it.
Step 2: Review the Date of Service (DOS) vs. Payer Receipt Date
Pull both key dates from your system:
- Date of Service (DOS): The date the patient was treated.
- Claim Receipt Date: The date shown in the payer’s or clearinghouse log.
If the claim was transmitted before the deadline but marked “late” by the payer, you can dispute it with proof of submission (see next step).
Step 3: Gather Proof of Timely Submission
This is the single most important part of overturning CO 146.
Acceptable proof includes:
- EDI 277CA acknowledgment showing initial transmission date.
- Clearinghouse batch confirmation with payer acceptance.
- Payer portal submission ID (if filed online).
- Email or fax confirmations from payer/MCO.
💡 Tip: Medicaid will not accept your internal EHR timestamps alone — you must show that the payer (or clearinghouse) actually received the claim within the deadline.
Step 4: Identify a Valid Exception Category
Each state allows only specific exceptions under 42 CFR §447.45(d)(4).
The most common include:
- Retroactive beneficiary eligibility.
- State or system administrative error.
- Provider enrollment or revalidation delay.
- Declared natural disaster.
- Medicare crossover delay (for dual-eligible patients).
If your claim fits one of these, attach documentation like eligibility notices, FEMA declarations, or enrollment letters.
Step 5: Submit a Timely Filing Exception or Reconsideration Request
| State | Form / Process | Deadline for Request |
|---|---|---|
| Florida | AHCA Form 2040 – Timely Filing Certification | Within 6 months of denial |
| Texas | TMHP Late Claim Appeal Form | Within 120 days of denial |
| Louisiana | Form 146 – Late Claim Certification | Within 180 days |
| New York | DOH Timely Filing Extension Request | Same quarter as denial |
| Illinois | HFS Provider Portal Appeal Submission | Within 180 days |
Attach all proof and keep copies of your submission.
Step 6: Track and Document the Reopening Case
After submission:
- Log the exception case number or appeal reference ID.
- Note who and when you sent the packet to.
- Store proof copies for compliance audits (many Medicaid agencies audit exception claims).
If no response is received within 30–60 days, follow up directly through the payer’s provider relations channel.
Step 7: Strengthen Future Workflows
To prevent recurring CO 146 denials:
- Implement claim aging alerts at 50%, 75%, and 90% of the filing window.
- Automate clearinghouse acknowledgment tracking for every Medicaid payer ID.
- Maintain a central “Timely Filing Matrix” for all your Medicaid and MCO partners.
- Train billing staff to rework RTPs or rejections within 7 days of notice.
A CO 146 denial doesn’t always mean lost revenue — but success depends entirely on documentation. If you can prove the claim was filed on time or meets an approved exception, many state Medicaid programs will reopen and pay it. The key is to act quickly, attach verifiable proof, and never let resubmissions linger past the state’s or plan’s correction window
Key Takeaways and Conclusion
Denial code CO 146 is one of the most common — and most preventable — Medicaid billing denials in 2025. It simply means the claim was submitted after the payer’s allowed filing window. Unlike Medicare’s universal 12-month rule (CO 29), Medicaid filing deadlines vary state by state and plan by plan, with many MCOs allowing only 90–180 days from the date of service. The key to preventing CO 146 denials is awareness and documentation. Providers must know each payer’s timeline, track every claim’s submission date, and maintain proof of timely filing — such as clearinghouse reports, EDI acknowledgments, and portal confirmations. When a claim denies late, the only chance of recovery lies in valid exceptions like retroactive eligibility, provider enrollment delays, or documented system errors.
In today’s tighter regulatory environment, state Medicaid agencies and MCOs are enforcing timely filing rules with greater precision. That’s why healthcare organizations need automated monitoring, state-specific expertise, and exception handling workflows to keep revenue flowing smoothly.
At MedStates, we specialize in identifying and resolving Medicaid timely filing denials like CO 146 — helping providers track submission timelines, manage exceptions, and prevent revenue loss before it happens.
👉 Contact MedStates today to protect your Medicaid reimbursements from timely filing denials and ensure your claims meet every 2025 filing rule — no matter the state or payer.
