Claim adjustment reason code
Denial code OA-100 meaning
CARC 100, usually seen as OA-100: The payer sent the payment to the patient or subscriber, not to the provider.
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- Reason code
- CARC 100
- Short name
- Paid to the patient
- Plain meaning
- The payer sent the payment to the patient or subscriber, not to the provider.
- Group codes
- OA-100: Other adjustment. An adjustment that is neither the provider's nor the patient's, often from coordination of benefits.
Plain-English summary written by Rivvi. X12 owns the CARC list and its exact wording, which is not reproduced here. Read it on the X12 CARC list (list dated November 1, 2025, checked October 23, 2026). This page does not decide how a claim is paid.
Common causes
- The provider does not accept assignment, or the plan pays members directly for out-of-network care.
What to check before resubmitting
- Collect the payment from the patient.
- Check that assignment of benefits is marked on the claim if you accept it.
Related reason codes
Related pages
Questions
What does denial code OA-100 mean?
The payer sent the payment to the patient or subscriber, not to the provider. This is Rivvi's plain-English summary of CARC 100. X12's exact wording is on x12.org.
How do I fix OA-100?
Collect the payment from the patient. Check that assignment of benefits is marked on the claim if you accept it.
Can I bill the patient for OA-100?
With group code CO, no. CO means the provider absorbs the amount under its contract or the payer's rules.
Which group codes come with CARC 100?
Most often OA (other adjustment). The group code, not the reason code, says who owes the amount.
What is the difference between a CARC and a RARC?
A claim adjustment reason code (CARC) says why a claim line was paid differently than billed. A remittance advice remark code (RARC) adds detail, such as which field is missing.