CO-104 is a withhold. The plan kept back part of the allowed amount under your managed care contract. It may pay some or all of it back later, often at a year-end settlement tied to cost or quality targets. It’s not a denial, and the patient never owes it. The risk is in the tracking. Practices that post CO-104 as a plain write-off lose sight of money that may still come back. Practices that don’t read the contract miss withholds taken on services that should be exempt. (Primary source: X12 Claim Adjustment Reason Codes)
In brief: CARC 104 reads “Managed care withholding.” Post it to a withhold account, not a write-off. Check that the contract allows a withhold on that service. Then match the year-end settlement to the total held back.
Part of our denial codes library. Written by Manikandan J, CPC, CRCR, who has reconciled managed care settlements for primary care groups. Published 21 October 2026. Last updated: 21 October 2026. Code wording is quoted word for word from X12.
X12 wording for CARC 104
| Field | X12 text |
|---|---|
| Code | 104 |
| Description | “Managed care withholding.” |
| Start | 01/01/1995 |
Source: X12 Claim Adjustment Reason Codes, checked 21 October 2026.
Example scenario (fictional names), part 1
CO-104 Denial Example: What Happened
Elena Brooks manages billing for Riverbend Family Medicine. Nurse practitioner Sam Doyle gave a flu shot to an adult patient (Z23). The claim listed 90686 for the vaccine and 90471 for giving it. The payer was Clearwater Health Plan, a fictional HMO with a withhold contract.
The 835 showed CAS*CO*104 on both lines, plus remark LQ*HE*N381. Elena knew Riverbend’s contract had a withhold. But she also remembered a list of services left out of it.
Did the CO-104 reason code belong on a vaccine claim at all? Keep reading, or jump to how the CO-104 denial was resolved.
How a withhold works
A withhold is a share of each payment the plan keeps back under the contract. A risk pool is the account where withheld money sits until the plan settles. A settlement is the year-end review that decides how much comes back. The amount returned often depends on targets, such as total cost of care or quality scores.
| Stage | What happens | What you see |
|---|---|---|
| Claim paid | Plan pays allowed minus the withhold | CARC 104 on the line |
| During the year | Money sits in the plan’s risk pool | Nothing on the remit |
| Settlement | Plan returns some, all or none | A settlement letter or remit; reversals may show N552 |
In Medicare Advantage, withholds are a kind of physician incentive plan. Federal rules on those plans are in 42 CFR 422.208.
Remark codes you may see
| RARC | X12 wording | When |
|---|---|---|
| N381 | “Alert: Consult our contractual agreement for restrictions/billing/payment information related to these charges.” | On the claim, pointing you to the contract |
| N552 | “Payment adjusted to reverse a previous withhold/bonus amount.” | When the plan gives back or takes back withheld money |
See the X12 RARC list for full wording.
How to handle CO-104 lines
- Post to a withhold account. Keep CARC 104 separate from contract write-offs so you can track it.
- Check the contract’s withhold terms. Note the rate and any services left out, for example vaccines, lab or drugs.
- Spot-check the math. Compare the held amount to the allowed amount and the contract rate.
- Dispute wrong withholds. If the service is exempt or the rate is wrong, send a payment dispute citing the contract section.
- Total it by year. Keep a running sum by plan and contract year.
- Match the settlement. When the plan settles, compare its figure to your total and ask for the detail.
Example scenario (fictional names), part 2
How the CO-104 Denial Was Resolved
Elena pulled the contract that N381 pointed to. The withhold exhibit listed vaccines and their admin codes as exempt. Clearwater’s system had applied the withhold to every line from the practice.
Fix: Elena filed a payment dispute for the vaccine claims of the past quarter. She attached the exhibit page and a list of claims. No corrected claim was needed, since the claim itself was right.
Outcome: Clearwater paid the withheld amounts back with N552 on the remit. Elena now runs a quick monthly check for CARC 104 on exempt codes.
Names and details are illustrative; no real patient data.
Worked example (illustrative)
A pediatric group gets a settlement letter saying it earned back part of its withhold. The billing manager’s log shows a larger total withheld than the letter lists. She asks the plan for claim-level detail. The plan finds that a block of claims was missed in the count, then sends a corrected settlement.
Common withhold mistakes
- Writing off CARC 104 as contract loss. You lose track of money that may come back.
- Not reading the exempt list. Withholds on exempt services are easy to miss.
- Waiting for the plan to report. Keep your own total so you can check the settlement.
- Billing the patient. The CO group means it’s never the patient’s share.
Related codes
- CO-45: charge exceeds the fee schedule or contracted amount.
- CO-24: charges covered under a capitation agreement.
- CO-253: sequestration reduction.
- CO-96: non-covered charges.
Key takeaways
CO-104 is money held back, not money lost for good. Post it to its own account, check that the contract allows it on each service, and dispute withholds on exempt codes. Keep a running total so you can check the year-end settlement line by line.
FAQ
What does CO-104 mean?
It means “Managed care withholding.” The plan kept back part of the payment under your contract.
Will I get CO-104 money back?
Maybe. It depends on the contract and on the targets measured at settlement.
Can I bill the patient for CO-104?
No. It’s a contract term between you and the plan.
What does N552 mean?
N552 means “Payment adjusted to reverse a previous withhold/bonus amount.” It shows up when withheld money is returned or taken back.
Can a plan withhold on every service?
Only if the contract says so. Many contracts exempt some services, such as vaccines or lab work.
How should I post CARC 104?
Post it to a separate withhold account so you can match it to the settlement.
Sources
How we checked: each code quote on this page was compared word for word with the X12 CARC and RARC lists on 21 October 2026.
- X12, Claim Adjustment Reason Codes (CARC 104, 24, 45, 253). Accessed 21 Oct 2026.
- X12, Remittance Advice Remark Codes (N381, N552). Accessed 21 Oct 2026.
- eCFR, 42 CFR 422.208, Physician incentive plans. Accessed 21 Oct 2026.
Last updated: 21 October 2026 ยท This page is educational and doesn’t replace your payer contracts.