What a Medical Billing Clearinghouse Does to Your Claims

A medical billing clearinghouse checks your claims, converts them to the HIPAA standard format and sends each one to the right payer, then carries the replies back to you. Federal law defines a health care clearinghouse by that translation work. Under 45 CFR 160.103, it turns nonstandard data into a standard transaction, or turns a standard transaction into the nonstandard format the receiving entity uses.

The day-to-day job is bigger. Clearinghouses "often perform general and payer-specific edits on claims," according to the Medicare Claims Processing Manual. Many also reformat data for different payers and handle acknowledgments, remittances, claim status checks and eligibility queries. That work makes a clearinghouse an active editor of your claims rather than a passive pipe. CMS adds that some companies calling themselves clearinghouses do no editing and act as a "telecommunication switch" that only moves transactions. Ask yours which edits it runs, and for which payers.

Clearinghouse rejection vs denial

A clearinghouse rejection is not a denial. A rejection stops a claim before any payer decides it, because the claim failed an edit at the clearinghouse or at the payer's front end. Medicare does not count a rejected claim as received, according to chapter 24 of the CMS manual. Its contractors need not give that claim a control number or a receipt date. A claim Medicare returns as unprocessable "is not denied" and has no appeal rights, per chapter 1. You correct it and send it again while the filing deadline keeps running. Medicare sends some of those returns on the remittance itself, still with no appeal rights. A denial comes after the payer has accepted the claim and adjudicated it, meaning decided what to pay. It arrives on the remittance with a claim adjustment reason code, and the payer's appeal clock starts.

How a clearinghouse turns your claim into an 837

The 837 is the HIPAA standard electronic claim. A professional claim uses the ASC X12 837 version 005010X222, adopted at 45 CFR 162.1102. An electronic claim you send a health plan has to go as a standard transaction, under 45 CFR 162.923, unless you enter it in the plan's own system. The same section lets a clearinghouse do that job for you as your business associate. Your practice management system does not have to produce the 837 itself. A clearinghouse may take the claim in another format, translate it into the standard and translate the replies back, under 45 CFR 162.930.

Payers cannot rewrite the standard, even in the trading partner agreement that governs your electronic transactions with them. That agreement may not add data fields the standard does not define, or change the meaning of the standard's implementation guide, under 45 CFR 162.915. A health plan also may not reject a standard transaction because it contains data the plan does not use, per 45 CFR 162.925. Payers still differ in the member and provider records they check claims against, and in the edits they add. That is what a clearinghouse's payer-specific edits are for.

Clearinghouse claim scrubbing: what gets checked before a payer decides a claim

Claim scrubbing is the check a claim gets before it reaches the payer. A clearinghouse does it with edits, front-end checks on a claim's format and content. A claim that fails one comes back to you as a rejection. Payers run front-end checks as well, and Medicare's run in two stages. Its translation software first checks each file's syntax against the 837 implementation guide and reports errors on a receipt called the 999 acknowledgment, according to CMS. Its front end then runs code set edits, Medicare-specific edits and duplicate submission checks. Each code set "is valid within the dates specified by the organization responsible for maintaining that code set," under 45 CFR 162.1011. Medical codes have to be valid on the date of service, under 45 CFR 162.1000. A code deleted before that date fails, and so does one that took effect after it.

Provider identifiers matter too. Your NPI has to appear on every standard transaction that calls for a provider identifier. You also have to require any clearinghouse working for you to use your NPIs as each transaction requires, under 45 CFR 162.410.

Commercial payers can add checks of their own. UnitedHealthcare's Smart Edits flag electronic data interchange (EDI) claims with potential errors, on top of the HIPAA edits the clearinghouse applies, according to its 2026 administrative guide. A claim that fails the HIPAA edits goes back to you to fix and resubmit. You have 5 calendar days to update a claim flagged by a Return or Documentation Smart Edit before it moves on to processing. A Rejection Smart Edit keeps the claim out of UnitedHealthcare's processing system until you act.

What clearinghouse edits do not catch

Clearinghouse edits test whether a claim is complete and valid, not whether the payer will pay it. A claim can pass every edit and still come back denied for coverage, medical necessity, a missing authorization or data that looks right but is wrong. Experian Health surveyed 250 healthcare professionals responsible for financial, billing or claims management decisions for its State of Claims 2025 report. Of those, 50% named missing or inaccurate claim data as a primary denial trigger. Authorizations came second at 35%, and incomplete or incorrect patient registration data third at 32%. Our post on the top 10 claim denial reasons covers each one.

Eligibility problems can come back as a rejection or a denial. UnitedHealthcare calls "incomplete or inaccurate eligibility information" one of the primary reasons for claims rejection. Its guide tells you to check eligibility and benefits before care, which also reduces denials for noncoverage. That check has its own HIPAA transaction, the 270/271, adopted at 45 CFR 162.1202. CMS lists eligibility queries among the work clearinghouses manage.

Clearinghouse acknowledgments: the 999 and the 277CA

The 999 and the 277CA are acknowledgments, the receipts that tell you where a claim stands. In Medicare's process, the 999 reports whether a batch of claims passed syntax checks, and the 277CA reports which claims Medicare accepted and which it rejected. Some 999 failures reject the whole batch. Errors that do not reject the batch pass to claim-level edits. Each accepted claim gets a claim control number, reported back on the 277CA, per chapter 24.

The same manual marks both acknowledgments "not required under HIPAA," so ask your clearinghouse which ones each of your payers returns. Watch the clock on them too. Medicare contractors may purge a 999 that nobody downloaded from the submitter's mailbox after five business days, per CMS. A clearinghouse acceptance tells you the clearinghouse took the claim. Only the payer's acknowledgment tells you the payer took it. If a claim does not appear in UnitedHealthcare's portal, its guide sends you to your clearinghouse reports and its rejection notices.

What happens when a clearinghouse rejects a claim

A rejected claim comes back to you and goes nowhere until someone corrects it and sends it again. Medicare treats a resubmitted rejected claim as an initial claim, per chapter 24. After a front-end return, Medicare keeps no data from the original, so you send the fix as a new claim, under chapter 1.

The filing deadline does not pause for a rejection. A Medicare claim "must be filed no later than the close of the period ending 1 calendar year after the date of service," under 42 CFR 424.44. UnitedHealthcare's filing limits vary by state requirements and contract. It will not accept a rejected claim as proof that you filed on time. Your proof has to show that the payer received and accepted the claim within your filing limit, according to its 2026 guide. A rejection nobody works becomes a late claim, and a late claim comes back as a CO-29 denial for missing the filing deadline. Medicare does not allow an appeal of that denial, per chapter 1.

A clearinghouse rejection never appears on the payer's remittance, so denial reports miss it. Work rejections the day they arrive. Our post on revenue cycle management steps for small practices covers giving every claim a live status.

How a clearinghouse routes claims and returns the 835 ERA

A clearinghouse routes each claim by payer ID and brings back the payer's 835 remittance. The payer ID "instructs the clearinghouse where to send your electronic claims," in UnitedHealthcare's words. Its guide warns that the payer ID on its list "may be different from the number issued by your clearinghouse," so settle any mismatch with the clearinghouse first.

The 835 is the HIPAA standard for remittance advice, adopted at 45 CFR 162.1602. It tells you what the payer paid on each claim, with adjustment codes that say why. Our post on denial management workflow design covers what the 835 contains and why to read it on arrival. Electronic remittance advice (ERA) needs its own enrollment. Medicare will not send ERA through a clearinghouse until you sign its ERA Enrollment Form. It returns remittance files either to you or to one receiver you designate, such as your clearinghouse, per chapter 24. UnitedHealthcare's guide calls Optum Pay its preferred method for direct deposit. Optum Pay also delivers remittance advice and 835 files, and it has its own enrollment.

Clearinghouse enrollment and switching: what Medicare requires

Clearinghouse enrollment is the paperwork that lets a clearinghouse exchange transactions with each payer for your practice. For Medicare, you sign the EDI Enrollment Form before the Medicare contractor will accept claims from you or your clearinghouse. The contractor checks that your NPI is active in PECOS, Medicare's provider enrollment system. The clearinghouse needs its own EDI number and password from each Medicare contractor and may not use yours. If you switch clearinghouses, you owe your Medicare contractor written notice in advance, including the date you stop using the old one. You sign the authorization that lets the new clearinghouse send and receive your transactions. The clearinghouse may not sign it for you, even under contract, per chapter 24.

Do you need a clearinghouse to submit claims?

HIPAA does not make you use a clearinghouse. It lets you "use a business associate, including a health care clearinghouse," to conduct standard transactions, under 45 CFR 162.923. The same section allows direct data entry into a health plan's own system. There you follow the standard's data content but not its format.

Medicare contractors offer free or at-cost software for sending HIPAA-compliant claims, according to CMS. Medicare also requires initial claims in electronic form under the Administrative Simplification Compliance Act. A physician practice with fewer than 10 full-time equivalent employees counts as small and can still file on paper, under 42 CFR 424.32. Going direct means a separate connection, enrollment and set of reports for each payer. A clearinghouse puts the connections and reports in one place, though payers such as Medicare still require their own enrollment.

Single-clearinghouse risk and the Change Healthcare outage

Depending on one clearinghouse means one outage can stop your claims, as the 2024 cyberattack on Change Healthcare showed. The attack began on February 21, 2024, according to CMS. Within weeks, CMS had directed Medicare contractors to speed up the steps providers needed to change clearinghouses, according to its March 9, 2024 statement. It also had them accept paper claims from providers who needed to file that way.

The attack took Change Healthcare, a health care electronic data interchange company, offline. Medicare made accelerated and advance payments to ease the cash flow disruption. CMS reported on June 17, 2024, that it had issued 4,722 advance payments totaling more than $717.18 million to Part B suppliers, including doctors. On July 31, 2025, Change Healthcare told the HHS Office for Civil Rights that the breach affected approximately 192.7 million individuals.

The risk is the dependency, not the clearinghouse. Know your fallback before you need it. List which payers you could reach through a second clearinghouse, a payer portal or your Medicare contractor's free or at-cost software, and how long each enrollment takes. Include the written notice and authorization Medicare requires when you switch clearinghouses.

Prior authorization through a clearinghouse: the 278 and CMS-0057-F

Prior authorization requests have their own HIPAA standard, the X12 278, adopted at 45 CFR 162.1302. UnitedHealthcare's guide lists referrals and authorizations (278) among the EDI transactions that run through a clearinghouse. CMS-0057-F is CMS's Interoperability and Prior Authorization final rule. It set decision deadlines starting in 2026 for Medicare Advantage organizations, Medicaid and CHIP fee-for-service programs and Medicaid and CHIP managed care plans. They must decide expedited requests within 72 hours and standard requests within seven calendar days. Medicare Advantage and Medicaid managed care plans can extend either deadline by up to 14 calendar days in limited cases, under 42 CFR 422.568, 422.572 and 438.210. The payers with those deadlines, plus insurers selling plans on the federal exchanges, must give a specific reason when they deny a prior authorization request. The requirements for a Prior Authorization API, an electronic link that takes requests and returns decisions, start in 2027. None of these requirements covers prior authorization for drugs.

Our posts on why prior authorization approval does not guarantee payment and on retro authorization cover what those changes mean for your claims. The clearinghouse can carry the request as a 278, and it carries the claim. The payer still checks at adjudication that the claim matches the approval.

EHR and clearinghouse integration: where claim data goes wrong

A clearinghouse can only check the data your EHR or practice management system sends it. If that data leaves the EHR incomplete, or picks up a typo when someone retypes it, the edits start from a bad copy. A member ID with one digit wrong or a misspelled name can trigger a rejection that has nothing to do with the care you billed.

Direct integration removes the manual export-and-import step, where transcription errors and delays creep in. Demographics, insurance details and authorization numbers then flow from the EHR into the claim instead of getting retyped. Clean data gets a claim through the edits. Payment depends on whether each service meets the payer's current policy, and that check belongs before submission too.

Altair runs the whole revenue cycle, from eligibility to payment posting. Its payer-specific checks add to the edits your clearinghouse already runs, and its in-house billers work every rejection and every denial. The practice owner sees every claim and every dollar as it moves, not in a monthly report. The practice hires no one and manages no one, and it keeps the EMR and clearinghouse it already uses. Every claim is checked against the payer's current policy before it goes out, so it holds up if the payer reviews it later, and the money stays with the practice. See how Altair checks claims before they go out.

A clearinghouse acceptance gets a claim to the payer's door. Follow every claim until the payer confirms it got in and the 835 shows what it paid.

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