Claims processing in healthcare is the system by which medical bills travel from a doctor’s office or hospital to an insurance company, get reviewed, and result in a payment or denial. Every time you visit a provider and insurance is involved, a claim is generated, submitted, checked for errors, evaluated against your policy, and either paid or rejected. In 2024, Massachusetts insurers alone processed 45.9 million claims, and roughly one in five was denied, mostly for administrative errors rather than medical reasons.
Understanding how this process works helps explain why a bill takes weeks to arrive, why you might get an unexpected balance, or why your provider’s office asks so many questions before your appointment even starts.
The Six Stages of a Claim’s Life
A healthcare claim follows a predictable path from the moment you check in for an appointment to the moment your insurance company sends payment. Each stage introduces a point where things can go smoothly or go wrong.
Eligibility verification happens before you’re even treated. Your provider’s office confirms that your insurance is active and that the planned service is covered. For certain procedures, this step also includes getting prior authorization from your insurer, essentially advance approval that the service is medically necessary and falls within your plan.
Claim submission begins after your visit. Your provider’s billing team translates what happened during your appointment into standardized codes for diagnoses and procedures, then packages that information into a claim form and sends it to your insurer. Most claims are submitted electronically, though paper claims still exist.
Adjudication is the insurer’s review. This is where the payer determines how much to pay, how much you owe, or whether to deny the claim entirely. It’s the most complex stage and is covered in detail below.
Payment posting occurs once the insurer makes a decision. The approved amount is sent to the provider (often by electronic funds transfer), and the provider records that payment against your account.
Patient billing follows if there’s a remaining balance after insurance pays its share. This is the bill you receive for copays, deductibles, coinsurance, or any services your plan didn’t cover.
Monitoring and follow-up is the ongoing work of tracking denied claims, filing appeals, and identifying patterns that cause repeated errors. Large healthcare organizations analyze denial trends to prevent the same mistakes from recurring.
How Electronic Claims Actually Move
The vast majority of claims travel electronically using formats mandated by HIPAA. The standard submission format is called the 837 transaction, which is the electronic equivalent of a paper claim form. It contains all the same data: patient demographics, insurance details, diagnosis codes, procedure codes, and provider identification numbers. When the insurer sends back payment information, it uses the 835 transaction, which functions as a digital explanation of benefits that can also trigger a direct deposit into the provider’s bank account.
Between the provider and the insurer sits a clearinghouse, a third-party service that acts as a gatekeeper. Before your claim ever reaches the insurance company, the clearinghouse scrubs it for errors. It checks that patient information matches, that procedure and diagnosis codes are valid, that required fields aren’t blank, and that the claim is formatted to meet the specific insurer’s requirements. Claims that fail these checks get bounced back to the provider for correction before the insurer ever sees them. This step catches a significant share of problems that would otherwise result in denials.
What Happens During Adjudication
Adjudication is where the insurer makes its decision, and it involves layered checks that happen largely through automated systems. The payer verifies that you were enrolled and eligible on the date of service, that the diagnosis and procedure codes are valid and match each other logically, and that the provider is credentialed and in-network (or that out-of-network benefits apply).
Next comes pricing. The insurer calculates the allowed amount based on its contract with the provider, then determines how much of that amount falls on you based on where you stand with your deductible and out-of-pocket maximum for the year. The system also checks for policy-specific rules: service limits, waiting periods, prior authorization requirements, and bundling rules that combine related procedures into a single payment.
Finally, integrity checks flag anything that looks like potential fraud, abuse, or duplicate billing.
A claim exits adjudication in one of five states:
- Paid in full at the billed or allowed amount
- Paid with adjustments due to contractual rates, policy limits, or bundling rules
- Denied for coverage, eligibility, medical necessity, or policy violations
- Pended because the insurer needs more information or manual review
- Rejected due to formatting or data errors that require correction and resubmission
Rejections vs. Denials
These two terms sound interchangeable, but they’re technically different and the distinction matters. A rejection means the claim never made it into the insurer’s processing system. It was kicked back at the door because of a formatting error, a missing provider identification number, or an invalid code. A rejected claim was never officially filed, so it can’t be appealed. It simply needs to be corrected and resubmitted.
A denial means the insurer accepted the claim, processed it, and decided not to pay. Denials can be appealed. Common denial reasons include lack of prior authorization, services deemed not medically necessary, or billing for something the patient’s plan doesn’t cover. If you or your provider disagrees with a denial, the appeals process typically has up to five levels, each with its own review and decision letter that explains how to escalate further. For Medicare, reaching the highest level of appeal (federal court) requires a minimum dollar amount of $1,960 as of 2026.
Why So Many Claims Get Denied
The denial rate in healthcare is strikingly high. Data from the Massachusetts Health Policy Commission found that the average denial rate across insurers was 20.4% in 2024. That means roughly one in five claims was denied.
The surprising part is the reason. Clinical denials, where the insurer says a service wasn’t medically necessary or was experimental, made up at most 1% of denials for any insurer. The overwhelming majority were administrative. About 11.7% of all claims were denied for “other administrative” reasons, meaning the provider didn’t meet the insurer’s procedural rules. Another 4.9% were denied for incomplete claims, coding errors, or duplicate submissions. Across all professional medical and surgical claims, 80% of denials were administrative in nature.
In practical terms, this means the system’s biggest failure point isn’t disagreements about medical care. It’s paperwork: missing information, wrong codes, duplicate filings, and procedural missteps. Many of these denials are preventable, which is why clearinghouses, automated scrubbing tools, and staff training have become central to healthcare billing operations.
The Claim Forms Behind the Process
Even though most claims are electronic, they’re built on the data frameworks of two standard paper forms. The CMS-1500 is used for professional claims, meaning services billed by individual practitioners like physicians, therapists, physician assistants, and medical equipment suppliers. It’s also the form used by ambulatory surgery centers, home health agencies, and behavioral health clinics.
The UB-04 is used for institutional claims, covering hospitals (inpatient and outpatient), skilled nursing facilities, hospice facilities, dialysis centers, and birthing centers. A third form, the ADA dental claim form, handles dental services specifically.
The electronic 837 transaction mirrors the data fields of these paper forms but transmits them digitally. The form type matters because it determines what information is required and how the insurer’s system processes the claim.
How Long Payment Takes
Federal rules set a clear timeline for Medicare claims. A “clean” claim, one that’s complete and error-free, must be paid within 30 calendar days of receipt. If the payer misses that deadline, it owes interest. This 30-day window applies to both electronic and paper claims.
Private insurers operate under state-specific prompt payment laws, which vary but generally require payment within 30 to 45 days for clean claims. The clock starts when the insurer receives the claim, not when the provider submits it. Claims that aren’t clean, those that need additional information or have errors, don’t fall under these timelines until the issues are resolved and the claim is resubmitted.
For patients, this means you typically won’t see a bill until well after your visit. Your provider submits the claim, waits for the insurer’s response, posts the payment, and then bills you for any remaining balance. That chain of events can easily stretch to 60 days or more, which is why a bill from a January appointment might not arrive until March.