CARC 166: These services were submitted after this payer's responsibility for processing claims under this plan ended.
These services were submitted after this payer's responsibility for processing claims under this plan ended.
CARC 166 appears on the 835 ERA (Electronic Remittance Advice) that the payer returns after claim adjudication. It explains a reduction, denial, or payment adjustment to your billing team. For your practice, the question is workflow: identify the pattern, route the denial to the right resolution path (rebill, appeal, write-off), and recover what's recoverable without burning RVU time on dead-end fights.
What CARC 166 means
The official X12 description is: “These services were submitted after this payer's responsibility for processing claims under this plan ended.”
In plain language: These services were submitted after this payer's responsibility for processing claims under this plan ended.
Practice workflow for CARC X 166
Verify the EOB details. If you believe the code is misapplied, contact the carrier's member services or your provider's billing office.
CARC 166 group codes explained
On the 835 ERA, CARC 166 appears alongside a group code that signals who is financially responsible for the adjustment. CO (Contractual Obligation) — Contractual write-off. The provider agreed to the rate. Patient does NOT owe this amount.
Frequently asked questions
What does CARC 166 mean?
These services were submitted after this payer's responsibility for processing claims under this plan ended. In plain language: These services were submitted after this payer's responsibility for processing claims under this plan ended.
Is CARC 166 appealable?
CARC 166 is usually not appealable on its own — it's typically a contractual, informational, or routine adjustment. Verify the EOB details. If you believe the code is misapplied, contact the carrier's member services or your provider's billing office.
Which group code does CARC 166 appear under?
CARC 166 most often appears under: CO (Contractual Obligation) — Contractual write-off. The provider agreed to the rate. Patient does NOT owe this amount.
What should I do if I see CARC 166 on the 835?
Verify the EOB details. If you believe the code is misapplied, contact the carrier's member services or your provider's billing office.
Related resources
Sources
Contact: hello@approvalhelp.com