CO 198 denial code

Claim adjustment reason code 198. Often reported as CO 198.

Authorization limits exceeded

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 198 means

An authorization was in place, but the claim went beyond what it allowed, such as more visits, units or days than approved.

Unlike a missing authorization, here the payer found one on file. The service billed goes past the approved quantity, date range or scope.

Therapy visits, home health visits, inpatient days and drug units are frequent examples. Often only the excess lines are denied while the approved portion pays.

Group codes seen with 198

On a remittance, 198 comes after a group code. These are the ones it is most often reported with:

• CO 198 (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.

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

• More visits or units were billed than the authorization approved.
• Services were provided after the authorization end date.
• The billed code or level of care was higher than the one authorized.

What to do next

1. Compare the claim lines with the approved units, dates and codes on the authorization.
2. Request an extension or additional units from the payer if care is ongoing.
3. Correct unit counts or dates if the claim overstated what was done, then resubmit.
4. Set up an alert on remaining authorized visits so staff request more before they run out.

Related codes

• 197 (reason code) No prior authorization on file
• 210 (reason code) Authorization not obtained in time
• 119 (reason code) Benefit maximum reached