5.2 NPI & EDI transactions (837/835/270/271/277CA/999)

The National Provider Identifier (NPI)

The NPI is a 10-digit numeric identifier assigned to every covered health care provider under HIPAA. It is issued through NPPES (the National Plan and Provider Enumeration System). The NPI is "intelligence-free" — the digits carry no embedded information about the provider's specialty, state, or type, so the number never changes when a provider moves or changes specialty. It replaced legacy identifiers such as the UPIN and payer-specific provider numbers, giving each provider one identifier for all payers. There are two entity types: Type 1 for individual providers (a single clinician) and Type 2 for organizations such as hospitals and group practices. The tenth digit is a check digit calculated with the Luhn algorithm so keying errors can be caught automatically. On the CMS-1500 the NPI appears in Item 33a (billing) and Item 24J (rendering); on the UB-04 it appears in FL 56. Providers apply for an NPI at no cost through NPPES, and each NPI is paired with a taxonomy code that classifies the provider's specialty on claims. A provider keeps the same NPI for life — even after changing employers or specialties — which is why payers, clearinghouses, and CMS all key their records to it.

HIPAA EDI transactions

HIPAA's Administrative Simplification rules require standardized electronic data interchange (EDI) using the ASC X12 format (the current version is 5010). Each transaction type has a number, and the CBCS exam expects you to match the number to its purpose and direction.

• 270 / 271 — Eligibility. The 270 is the inquiry a provider sends to verify a patient's coverage and benefits; the 271 is the payer's response listing copay, deductible, and covered services.
• 837 — Health Care Claim. The electronic equivalent of the CMS-1500 or UB-04. Its variants are 837P (professional), 837I (institutional), and 837D (dental).
• 276 / 277 — Claim status. The 276 is the provider's inquiry about the status of an already-submitted claim; the 277 is the payer's status response.
• 277CA — Claim Acknowledgment. A response that confirms whether each claim was accepted or rejected at the front end, before adjudication. It reports on claim content, not just the file.
• 278 — Referral / prior authorization request and response.
• 835 — Health Care Claim Payment/Advice, the electronic remittance advice (ERA). It reports how the claim was adjudicated — paid, adjusted, or denied — and usually pairs with an electronic funds transfer (EFT) deposit.
• 999 — Functional Acknowledgment. Confirms that the EDI file was received and passed a syntax check (accepted or rejected for format); it replaced the older 997.
• TA1 — Interchange Acknowledgment. Reports on the validity of the interchange envelope itself — the outermost wrapper — flagging a corrupted or misaddressed file before its contents are read.

EDI transactions table

How the transactions flow

A typical electronic workflow chains these transactions together. Before the visit, the office sends a 270 and reads the 271 to confirm the patient is eligible and to learn the copay and deductible. After the encounter is coded, the biller transmits an 837 claim. The receiver first returns a TA1 if the envelope is malformed, then a 999 to confirm the file's syntax passed, and then a 277CA to state whether each individual claim was accepted for adjudication or rejected. If a claim seems delayed, the biller sends a 276 and reads the 277 for status. When the payer finishes adjudication, it returns an 835 ERA describing the payment, contractual adjustments, patient responsibility, and any denials — usually accompanied by an EFT deposit. Posting the 835 to patient accounts closes the loop.

Standards and covered entities

These transaction standards are mandatory for covered entities — health plans, health care clearinghouses, and providers who bill electronically. All must use the same ASC X12 5010 formats and standard code sets so that a claim built once can be understood by every payer. This uniformity is the whole point of HIPAA Administrative Simplification: it eliminates the many proprietary formats that once existed and lets a clearinghouse translate a single 837 into whatever format each payer accepts.

Why the numbers matter

Confusing these numbers is a common exam trap. Remember that the 837 goes out (the claim) and the 835 comes back (the money). The 270 asks about eligibility and the 271 answers; the 276 asks about status and the 277 answers. The 277CA is a specialized acknowledgment, not a full status response. Keep the three acknowledgment layers straight: the TA1 is about the envelope, the 999 is about file syntax, and the 277CA is about claim content. Remembering the inquiry/response pairs — 270/271 and 276/277 — and the escalating acknowledgment layers will earn several points on the billing portion of the CBCS.