CO-249 lands on a hospital stay that the payer linked to an earlier one. The plan thinks the second admission was part of the first episode of care. It will not pay a second DRG unless you show otherwise. Some readmissions really should be combined. Others were unrelated and only need the right code or the right records. (Primary source: X12 Claim Adjustment Reason Codes)
In brief: CARC 249 reads “This claim has been identified as a readmission. (Use only with Group Code CO)”. Compare the two stays. If the return was related and on the same day, combine them on one claim. If it was unrelated, report condition code B4 on a same-day return or appeal a longer gap with the records.
Part of our denial codes library. Written by Manikandan J, CPC, CRCR, who has reviewed inpatient readmission edits and DRG claims for health plans. Published 24 October 2026. Last updated: 24 October 2026. Code wording quoted word for word from X12.
Official wording and what it covers
| Field | Value |
|---|---|
| Code | 249 |
| Description | “This claim has been identified as a readmission. (Use only with Group Code CO)” |
| Start | 09/30/2012 |
Source: X12 Claim Adjustment Reason Codes, checked 24 October 2026.
A readmission is a new inpatient stay soon after a discharge. Each payer sets its own window. Medicare’s rules are in the Claims Processing Manual, chapter 3, section 40.2.5. A same-day return to the same PPS hospital for a related condition must be combined with the first stay. A same-day return for an unrelated condition carries condition code B4.
CO-249 is different from the Hospital Readmissions Reduction Program. That program lowers a hospital’s payments based on its readmission rates. It does not deny single claims.
Example scenario (fictional names), part 1
CO-249 Denial Example: What Happened
Grace Okafor works inpatient billing at Northfield General, a fictional acute care hospital. A patient went home after a pneumonia stay on 2 October and was back that evening after a fall at home broke her hip.
The hip fracture stay came back with CAS*CO*249 and no payment. The payer had linked it to the pneumonia stay.
Should Grace combine the two stays, or was this a separate admission? Keep reading, or jump to how the CO-249 denial was resolved.
Why payers flag readmissions
- Same-day return, related condition. The two stays should be one claim, so the second one is denied.
- Same-day return, unrelated condition. The second claim did not carry condition code B4.
- A plan window. For example, a commercial contract may review any return within a set number of days.
- Early discharge concerns. The payer suspects the first discharge was premature.
- Planned readmission. A staged procedure was planned at discharge but not documented as planned.
How to fix CO-249
- Line up both stays. Compare discharge and admit dates, the principal diagnoses and the discharge summary.
- Decide if they are related. Ask whether the return was for symptoms of the first condition or for its follow-up care.
- Related, same day: adjust the first claim to include both stays, and do not bill the second stay on its own.
- Unrelated, same day: add condition code B4 in FL 18-28 on the claim whose admission date equals the prior discharge date. Send a replacement claim, type of bill 0117 with the original claim number in FL 64.
- Longer gap or planned stay: appeal with both discharge summaries, showing a new condition or a documented plan.
If the payer asks for records, our medical necessity documentation guide explains what reviewers read first.
Example scenario (fictional names), part 2
How the CO-249 Denial Was Resolved
Grace read both charts. The first stay treated pneumonia, J18.9, and the second treated a right hip fracture after a fall at home, S72.001A, so the conditions were unrelated.
Fix: She sent a replacement claim for the hip stay with condition code B4 in FL 18, type of bill 0117 and the original claim number in FL 64.
Outcome: The fracture stay paid its own DRG. Northfield added a pre-bill check for any admit date that equals a recent discharge date.
Names and details are illustrative; no real patient data.
CMS-1500 not shown: CO-249 is an inpatient facility edit on the UB-04; physician claims for each stay are not affected.
- FL 18: condition code B4 added (admission unrelated to the same-day discharge).
- FL 4 + FL 64: type of bill 0117 (replacement) with the original claim number.
- FL 12: admission date 100226 is unchanged; it equals the prior discharge date.
- FL 67: S72.001A (entered as S72001A) is unchanged.
- CMS-1500: no change; physician claims are not part of this edit.
CO-249 compared with similar codes
| Code | What it means | Main fix |
|---|---|---|
| CO-249 | Stay flagged as a readmission | Combine, add B4, or appeal |
| CO-50 | Not medically necessary | Records and appeal |
| CO-18 | Exact duplicate claim | Check the first claim |
| CO-151 | Number of services not supported | Documentation |
FAQ
What does CO-249 mean?
The payer linked this inpatient stay to an earlier one and will not pay it as a separate admission.
What is condition code B4?
It tells Medicare a same-day readmission was unrelated to the prior stay. It goes in FL 18-28 on the UB-04.
Does CO-249 apply to physician claims?
Rarely. It is a facility edit. Professional services during each stay are billed as usual.
Can I bill the patient for CO-249?
No. The group code is always CO, so the hospital carries the adjustment.
How long is the readmission window?
It depends on the payer. Medicare combines related same-day returns, while many commercial contracts set their own windows.
Sources
How we checked: the code quote on this page was matched word for word with the X12 CARC list on 24 October 2026.
- X12, Claim Adjustment Reason Codes (CARC 249). Accessed 24 Oct 2026.
- CMS, Medicare Claims Processing Manual, chapter 3. Accessed 24 Oct 2026.
- CMS, Hospital Readmissions Reduction Program. Accessed 24 Oct 2026.
- NUBC, National Uniform Billing Committee. Accessed 24 Oct 2026.
Last updated: 24 October 2026 · Educational content; not legal advice.
Related denial codes
- CO-239: Rebill Separate Claims by Coverage Period
- CO-233: Hospital-Acquired Conditions
- CO-232: Institutional Transfer Amount
- CO-267: Claim Spans Multiple Months
- CO-274: Paid Through a Care Coordination Arrangement
- CO-190: Payment Included in the SNF Qualified Stay
- CO-186: Level of Care Change Adjustment
- CO-135: Interim Bills Cannot Be Processed