CAS segment of the 835 immediately before the CARC. They indicate how the payer classified an adjustment and who may be responsible for the amount.
The four codes
Why the group code matters
Group-code mapping determines how adjustments reach the patient ledger.- Posting a PR amount as CO can prevent a valid patient balance from entering the statement cycle.
- Posting a CO amount as PR can cause the practice to bill an amount that its payer contract requires it to absorb. That may create a contract, compliance, and patient-service problem.
CO, contractual obligation
The most common group code. The provider absorbs the amount because the participation agreement says so.
When CO-197 reports a missing authorization as a contractual obligation, the practice will generally need to absorb the amount unless the contract and applicable patient-notice rules permit another result. Confirm the authorization history and the plan terms before moving any balance to the patient.
PR, patient responsibility
The payer reports the amount as patient responsibility. Confirm any contract or notice requirements before moving it to the patient ledger and statement cycle.Downgrades: watch where the difference lands
When a plan prices a service at an alternate benefit, such as a posterior composite at an amalgam allowable, the remittance allocates the difference through the same group codes used for other adjustments. Plans and participation agreements differ on how much becomes patient responsibility. Read the actual remittance and the plan’s alternate-benefit clause before billing the patient, and include known downgrade behavior in treatment-plan estimates. See Denials vs downgrades.OA, other adjustment
Used where neither CO nor PR applies. Frequently informational, or a transfer.PI, payer initiated reductions
The payer reduced payment based on its own determination rather than identifying the amount as a contractual obligation. Review the CARC, RARC, plan policy, and contract to determine whether an appeal is available. PI adjustments are less common than CO and PR adjustments and should generally enter a review queue rather than being written off automatically.Quick reference: can I bill the patient?
Configuration checklist
For your auto-posting setup:- CO → contractual adjustment write-off account
- PR → patient ledger, into the statement cycle
- OA-23 on a secondary claim → informational, not an adjustment
- OA-100 → patient recovery workflow
- PI → review queue, not auto-write-off
- Any group code with a $0 payment and a denial CARC → denial queue, not write-off
- PLB segments → handled separately from claim-level adjustments