CO-228 denial code
Denied for failure to supply requested information to a previous payer
How to fix it
Resolve the outstanding request with the previous payer first, then rebill.
How to prevent it
Do not let primary payer requests age; they block secondary payment as well as primary.
In practice
A primary payer requested records and received no response, so it never completed adjudication. The secondary claim is submitted anyway and returns CO-228.
The blockage is upstream. Until the primary's request is satisfied and the claim adjudicates, the secondary has nothing to coordinate against and will not pay.
Resolve the outstanding request with the primary first, obtain the completed adjudication, and then rebill the secondary with the remittance attached.
What sits behind it
The compounding effect is what makes this expensive. One unanswered request stalls the primary claim, the secondary claim behind it, and any patient billing that depends on knowing the final balance, so a single administrative gap freezes the whole account.
It is also a signal worth acting on. A secondary denial citing an unanswered primary request means a primary request was missed, and where one was missed others usually were too. Checking for related open requests at the same time is efficient.
Filing deadlines run for both payers throughout. The primary's clock runs from the date of service and the secondary's typically from the primary's adjudication date, which means a stalled primary can quietly consume the whole window for both.
Related codes
Terms used here — Coordination of Benefits · Timely Filing · Appeal
How we handle it — Denial Management · AR Management · Claims Management
Primary sources
The rules behind CO-228, at the bodies that publish them.
- Evaluation and Management services guide (opens in a new tab)
Centers for Medicare & Medicaid Services — How E/M level is determined under the current medical decision making and time rules. The reference for any dispute about whether documentation supports a level.
- Medicare Claims Processing Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — The operative manual for how Medicare claims must be coded, submitted, adjusted and appealed. When a payer policy and a vendor's advice disagree, this settles it.
- Medicare claims appeals process (opens in a new tab)
Centers for Medicare & Medicaid Services — The five levels of appeal, what each requires and the deadline for each. Missing a level's deadline ends the appeal regardless of the claim's merits.
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-228
No. The secondary calculates its liability from the primary's adjudication, and until that adjudication completes there is nothing to coordinate against. The request has to be satisfied with the primary before the secondary claim can go anywhere.
That a primary request was missed, which usually means others were too. Checking for related open requests when this arrives is efficient, because the same routing gap that lost one request has probably lost several.
Both clocks run throughout. The primary's deadline runs from the date of service and the secondary's typically from the primary's adjudication date, so a stalled primary can consume the available window for both payers at once.
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