How it works
Under HIPAA’s electronic transaction standards, health plans must accept claims in the 837 format, and most practices submit almost all claims this way, usually through a clearinghouse. The 837P carries the same information as the paper CMS-1500 form; the 837I corresponds to the UB-04. The clearinghouse checks format and payer-specific rules and returns acknowledgments showing whether each claim was accepted.
Why it matters
Electronic claims are processed faster than paper and produce acknowledgments that serve as proof of timely filing. Most rejections at this stage are data problems — subscriber IDs, provider identifiers, missing fields — that can be prevented at registration and claim setup.
Example
A physician practice sends an 837P for an office visit. Within a day, a 277CA acknowledgment shows it was accepted for processing; about two weeks later, an 835 arrives with the payment. See medical billing explained.