CO 78 denial code

Claim adjustment reason code 78. Often reported as CO 78 or PR 78.

Non-covered days or room charge

Unofficial reference. This is our own plain-English explanation, not the official code text. Payer rules differ. Verify with the payer and the official X12 code list. AlphaPrefix is not affiliated with X12, CMS or any payer. Data last updated Nov 11, 2026.

What 78 means

Part of an inpatient stay was not paid because some days or the room charge for them were not covered.

The payer decided that certain days of the stay, or the room and board charge tied to them, fall outside coverage. Common reasons are days after the patient no longer needed inpatient care, days beyond a benefit limit, or a private room billed without medical need.

The group code tells you who carries the amount. PR usually means the patient was properly notified or the plan limit was reached, while CO points to a provider liability.

Group codes seen with 78

On a remittance, 78 comes after a group code. These are the ones it is most often reported with:

• CO 78 (Contractual Obligation): The provider's side of the ledger. The reduction comes from the payer contract or a rule the provider has to follow, and the patient normally cannot be billed for it.
• PR 78 (Patient Responsibility): The amount is assigned to the patient. Deductibles, coinsurance and copays are the everyday examples. Whether you can collect it still depends on your contract and the patient's plan.

The payer chooses the group code for each adjustment, so the same reason code can appear with another group code on your remittance. Read the two together. More about group codes.

Common causes

• The patient stayed on after inpatient level of care was no longer needed, such as while waiting for placement.
• The patient used up the plan's covered inpatient days for the benefit period.
• A private room was billed without documentation that it was medically necessary.
• Leave of absence or administrative days were billed as covered days.

What to do next

1. Compare the covered and non-covered days on the remittance with the stay and the utilization review notes.
2. Check whether the patient received a valid liability notice before the non-covered days began.
3. Appeal with clinical documentation if the days met inpatient criteria.
4. Confirm room type and accommodation revenue codes match what was ordered and documented.

Related codes

• 119 (reason code) Benefit maximum reached
• 96 (reason code) Service not covered by the plan
• 69 (reason code) Day outlier adjustment