Clearinghouses

How it works

Everything a provider exchanges with a payer travels as a standardized X12 EDI transaction. This is machine-to-machine billing data in formats mandated under HIPAA. The clearinghouse behaves as the switchboard for that traffic. The core transactions it handles:

• 837 — the claim. The provider's billing system produces an 837 (professional, institutional, or dental) containing patient, provider, diagnosis, procedure, charge, and coordination-of-benefits data. The clearinghouse validates it, applies payer-specific edits, and forwards it for adjudication.
• 270/271 — eligibility. The provider sends a 270 asking "is this patient covered, and for what?" The clearinghouse routes it to the payer and returns the 271 with coverage status, copays, deductibles and accumulators, and benefit details. See Eligibility & Enrollment.
• 276/277 — claim status. A 276 asks "where is my claim?"; the 277 answers received / pending / paid / denied. A 277CA acknowledgment reports claim-level acceptance or rejection.
• 835 — remittance (ERA). The Electronic Remittance Advice tells the provider what was paid, denied, and adjusted, line by line, for automated cash posting in Revenue Cycle Management (RCM).
• 278 — prior authorization. The request-and-response transaction for Prior Authorization decisions, increasingly the focus of regulators (see below).
• 834 / 820 — enrollment and premium. Used between employers, exchanges, and payers to enroll members and remit group premium.

The clearinghouse's real value is the middle step: scrubbing and translation. It runs each transaction through thousands of edits — missing fields, invalid codes, member-ID mismatches, payer-specific quirks — and returns errors back to the provider before the payer sees them. A clean claim adjudicates faster and denies less. It also normalizes formats: every payer has its own companion guide, and the clearinghouse attempts to absorb that complexity so the provider doesn't have to.

Why it matters

Without clearinghouses, every one of ~6,000 hospitals and hundreds of thousands of practices would need a direct EDI connection to every one of thousands of payers — an N×M mesh that is impossible to maintain at the local level. The clearinghouse collapses that into a hub-and-spoke model: connect once, reach everyone. They are the connective tissue of the money flow, and they sit on a chokepoint — if the switch goes down, claims and cash stop.

That chokepoint became national news. The largest US clearinghouse — acquired by a unit of a major vertically integrated payer in a deal that closed in late 2022 after the Department of Justice unsuccessfully sued to block it. The clearinghouse processes roughly one-third of all US medical claims. In February 2024 a ransomware attack forced it offline for weeks. Providers couldn't submit claims or verify eligibility, cash flow froze across the system, and the government stood up emergency advance-payment programs. It was the clearest possible demonstration that a back-office plumbing layer most patients have never heard of is systemically critical infrastructure.

Who is involved

• Providers and RCM teams / billing vendors — the senders. Many practices reach a clearinghouse through their practice-management or EHR system rather than directly.
• Payers, TPAs, and their core claims engines — the receivers, who often prefer transactions to arrive pre-scrubbed.
• Clearinghouses and "switches" — some sell direct to providers; others operate wholesale, connecting other clearinghouses and vendors to payers.
• Regulators — HIPAA sets the transaction standards; the CMS Interoperability & Prior Authorization Final Rule (CMS-0057-F) pushes API-based prior authorization that could route around traditional EDI over time. See CMS (Centers for Medicare & Medicaid Services).

Numbers that matter

• ~95% of provider claims are now submitted electronically as X12 837 transactions, not on paper.
• The largest clearinghouse alone processes on the order of billions of transactions per year and touches a large share of all US claims.
• During the 2024 outage, surveys reported the overwhelming majority of affected practices saw a >20% revenue impact, underscoring how thin provider cash buffers are when the pipe stops.

Related

• The Stakeholders
• EDI & X12 Transaction Standards
• The Claims Lifecycle
• Revenue Cycle Management (RCM)
• Eligibility & Enrollment
• Payers (Health Plans)
• Third Party Administrators (TPAs)
• HIPAA
• The CMS Interoperability & Prior Authorization Final Rule (CMS-0057-F)
• EHRs & the Provider Tech Stack
• Prior Authorization
• How Money Flows

Sources

• CMS, Administrative Simplification — Transaction standards (HIPAA-mandated X12 transactions): https://www.cms.gov/priorities/key-initiatives/burden-reduction/administrative-simplification/transactions
• X12, Health Care Transaction Flow (270/271, 276/277, 278, 837, 835): https://x12.org/flow/health-care
• HFMA, "Cyberattack on Change Healthcare brings turmoil to healthcare operations nationwide": https://www.hfma.org/technology/cybersecurity/cyberattack-on-change-healthcare-brings-turmoil-to-healthcare-operations-nationwide/
• Office of Financial Research Brief, "The Cyberattack on Change Healthcare": https://www.financialresearch.gov/briefs/files/OFRBrief-24-05-change-healthcare-cyberattack.pdf
• Holland & Knight, "Change Healthcare Cybersecurity Incident: Financial Impact and Resulting Litigation": https://www.hklaw.com/en/insights/publications/2024/06/change-healthcare-cybersecurity-incident-financial-impact
• The Source on Healthcare Price and Competition, "DOJ's Challenge of the UnitedHealth and Change Healthcare Merger": https://sourceonhealthcare.org/dojs-challenge-of-the-unitedhealth-and-change-healthcare-merger-what-went-wrong-and-what-does-it-mean/