9 Most Common Medical Billing Errors and How to Fix Them

The most common medical billing errors are not clinical mistakes — they are data and coding mistakes made before the claim ever reaches a payer. A claim can be clinically perfect and still come back denied because the biller typed a 0 where the patient's card showed an O, or the code went out without the modifier that justified it.

Denials like these are getting more common. In Experian Health's State of Claims 2025 survey, 41% of providers said more than 10% of their claims are denied, up from 30% in 2022.

The encouraging part is how predictable the causes are. Nine mistakes account for the bulk of rejected claims, and each one below has a clear cause, the reason code you will see on the remittance, and a fix.

Why Billing Errors Are Getting More Expensive

Denials are climbing on two fronts at once. Experian's 2024 survey found almost three in four providers saying claim denials were increasing, and the trend has held: the share reporting denials on more than 10% of claims went 30% in 2022, 38% in 2024, 41% in 2025.

The cost of fixing them is just as steep. Premier's 2024 survey of 516 hospitals and health systems found that nearly 15% of claims to private payers are denied on first submission. The organizations are larger than a pediatric practice, but the denial mechanics are the same ones a practice works every week.

Working those denials is slow. Premier found providers needed an average of three rounds of review with insurers, each cycle taking 45 to 60 days, leaving some health systems unable to recoup costs for up to six months after care was delivered.

Some denied claims are never fully pursued, so a fixable error turns into lost revenue. Catching the mistake before the claim goes out costs far less than chasing it afterward.

The 9 Most Common Medical Billing Errors

The errors below account for most denied claims. Each is common, has a clear cause, and a fix you can put in place to get things back on track.

1. Incorrect or Incomplete Patient Information

One of the most frequent errors is also the most basic: a misspelled name, an incorrect birth date, or a mistyped insurance ID.

Payers use these details to match a patient to an active policy, so one mismatch stops the claim cold. It often returns under CARC 31, "patient cannot be identified as our insured."

How to avoid it: Verify demographics and insurance at every visit, including for returning patients, and confirm the details against the card directly, since the stored record may be out of date. Pediatrics adds a wrinkle: the child is the member and the parent is the subscriber, and claims are routinely denied when the child's name and birth date get entered in the subscriber fields instead.

2. Eligibility and Coverage Lapses

Coverage that looked fine at booking can lapse by the date of service if a parent switches jobs, a Medicaid renewal is missed, or a plan terminates at month's end. The visit happens, the claim goes out, and the denial is the first anyone hears that the policy wasn't active.

How to avoid it: Run an eligibility check before the visit, while there's still time to sort out coverage or reset the patient's expectations. Learning about a lapse now beats learning about it weeks later from a denial.

3. Coding Errors

Coding errors take a few forms. An outdated or mismatched CPT or ICD-10 code is one. Another is a diagnosis that doesn't justify the procedure, which payers flag as failing medical necessity. These usually trace back to thin documentation, a missed code update, or a coder reading an unclear note.

How to avoid it: Keep code sets current, tie every code to documentation that supports it, and run periodic coding audits to catch drift before it becomes a pattern.

4. Missing or Mismatched Modifiers

Modifiers tell the payer that two services were distinct, or that a procedure was altered. Without them, a claim can read as incomplete or duplicative.

When a procedure code goes out with the wrong modifier, or without one it needed, the claim is often denied under CARC 4 (Group Code CO), which covers a procedure code that is inconsistent with the modifier used.

Unbundling trips practices up the same way. The National Correct Coding Initiative publishes procedure-to-procedure edits identifying code pairs payers expect to be billed as one, so reporting two of those services separately without modifier 59 draws a denial. A same-day well child visit and sick visit works differently: it is not an NCCI pair, but the sick-visit E/M needs modifier 25 to be paid.

How to avoid it: Learn which of your routine services need modifiers, and build a check into your review so a claim doesn't go out missing one.

5. Duplicate Claims

Submitting the same service twice for the same patient, provider, and date draws a duplicate denial (often CARC 18, Group Code OA). It usually happens when staff resubmits a claim they weren't sure had gone through, or the same visit gets billed from two systems.

How to avoid it: Track claim status before resubmitting, and let a claim scrubber flag potential duplicates before they reach the payer.

6. Missing Prior Authorization

Some services need the payer's approval before they happen. Without it, the claim is denied regardless of whether the care was necessary, typically under CARC 15 or CARC 197 (Group Code CO).

How to avoid it: Handle insurance verification by confirming which services require authorization for each payer, and track requests so nothing gets performed before approval lands.

7. Insufficient Documentation

If the record doesn't support the service, the payer treats it as not performed. Medical necessity and documentation denials are among the hardest to overturn, because fixing them means proving something after the fact.

How to avoid it: Document to the level the code requires at the point of care, so the note stands on its own if a payer asks for it. A system that carries the documentation straight into the charge removes the gap where the note and the claim drift apart.

8. Missing the Filing Deadline

Every payer sets a filing window, and a claim submitted after is automatically denied, even when everything else is correct (CARC 29). Medicare, for instance, allows 12 months from the date of service.

How to avoid it: Know each payer's deadline and work your claims and rejections promptly, so nothing ages out while it sits.

9. Coordination of Benefits Errors

When a patient has more than one plan, billing the wrong one first triggers a coordination-of-benefits denial (CARC 22). It's common when a practice doesn't know a secondary plan exists or has the order reversed.

In pediatrics this is usually a Medicaid question. Under federal law Medicaid is the payer of last resort, so any commercial plan a child is on — a non-custodial parent's policy, a step-parent's plan, a grandparent's coverage — has to be billed and adjudicated first. A practice that does not know the second plan exists bills Medicaid first and gets a CARC 22 back.

How to avoid it: Ask about secondary coverage at registration and confirm which plan is primary before the claim goes out.

Building a Practice That Prevents Denials

Individual fixes matter, but the durable gains come from applying a few habits to every claim rather than fixing errors one at a time:

• Verify eligibility early: Check coverage before the visit, while there's still time to fix a problem.

• Scrub before submitting: Let a claim scrubber catch coding and modifier errors while the claim is still in your system.

• Track denials by reason code: A recurring CARC becomes a training fix, so the same denial stops showing up.

• Connect documentation to billing: When the note and the claim carry the same story, fewer charges fall apart.

Where Pediatric Billing Trips Up

Pediatric practices make every error above, plus a set stemming from how children's visits are coded. Generic billing advice misses these, and they appear as pediatric-specific denials.

• Newborns billed before they have an ID: A newborn often arrives for the first visit with no member ID and sometimes no legal name on file. The claim goes to the mother's policy, and coverage back-dates to the date of birth. But if the parent misses the payer's enrollment window to add the baby, usually 30 days, that retroactive coverage disappears and visits already delivered land on the family's balance.

• Same-day well child and sick visits: When a child is seen for a well child visit and an acute problem at a single visit, the sick-visit service requires modifier 25 and clearly separated documentation; otherwise, the second charge is denied.

• Vaccine administration coding: Immunization admin codes (90460 and 90461) apply through 18 years of age and require counseling by the provider, with 90460 covering the first component and 90461 each additional one. A mismatch results in a lower-paying code or a denial.

• Screening documentation: CPT 96110 covers developmental screening with scoring and documentation per standardized instrument, so a note that records a screen without naming the tool or capturing the score is an unbillable one. When more than one instrument is administered at the same visit — a developmental screen and a behavioral one, say — each goes on its own line with modifier 59, or the second is bundled away. On a Medicaid-weighted panel this matters: developmental screening is a required EPSDT component and 47 state Medicaid programs pay 96110 separately from the well child visit.

• Medicaid coordination of benefits: Many pediatric panels carry a large Medicaid share, where secondary-coverage rules and frequent eligibility changes make coordination-of-benefits errors more likely.

Cleaner Pediatric Claims by Design

Most of these errors stem from the same root cause: the record and the claim live in separate systems, so an error in one isn't caught until the other fails.

Keeping the record and the claim in sync is easier when both run on one platform built for how pediatric practices bill. Develo is the AI-native pediatric operating system built solely for independent pediatric practices, unifying charting, billing, practice management, and family engagement in one modern system.

With Develo, pediatric practices can:

• Capture and verify demographics and insurance at registration, so the details on the claim match the details on the card

• Apply age-based codes, vaccine administration codes, and the modifiers each requires from what was documented at the visit, through pediatrics-optimized automated charge capture

• Get prompted for modifier 25 when a well child visit and a sick visit happen on the same day

• Check eligibility against the plans a children's practice bills most often, including Medicaid

• Capture developmental screening results already scored, in a form that supports the charge

• Flag potential duplicates and missing modifiers before a claim reaches the payer

• Age claims against each payer's filing window, so a claim in process doesn't quietly run past its deadline

• Manage coordination of benefits across a child's plans, so the primary is billed first and the secondary follows automatically

• Track denials by reason code through deep revenue cycle reporting, turning a repeat rejection into a one-time fix

• Keep documentation and billing in a single flow, so the note and the claim carry the same story

Book a demo to see how Develo keeps pediatric claims clean from the first visit.

Frequently Asked Questions

What Is the Most Common Medical Billing Error?

One of the most common medical billing errors is incorrect or incomplete patient information, like a misspelled name, wrong birth date, or mistyped insurance ID. Because payers use these details to match a patient to coverage, a single mismatch is enough to stop the claim.

What Are the Top Denials in Medical Billing?

The most frequent denials trace to patient identification, eligibility, and coding. On a remittance they appear as reason codes: CARC 31 for an unmatched patient, and CARC 29 once the filing deadline has passed.

What Is a Claim Scrubber?

A claim scrubber is software that checks a claim against payer rules before submission, flagging missing modifiers, mismatched diagnosis and procedure codes, and likely duplicates.It catches the errors that would otherwise come back as denials weeks later. A scrubber loaded with pediatric payer rules — vaccine components, same-day modifiers, age-based codes — catches the ones a generic rule set lets through.

How Can a Practice Reduce Billing Errors?

A practice reduces billing errors by verifying eligibility before visits, running claims through a scrubber before submission, keeping code sets current, and tracking denials by reason code. Fixing an error before the claim leaves the office is far cheaper than appealing a denial later.

Why Do Pediatric Practices See Specific Billing Errors?

Pediatric practices see specific errors because children's visits use age-based codes, same-day well child and sick visit modifiers, vaccine administration coding, and Medicaid coordination of benefits. A generic billing setup handles these poorly, so a pediatric-built system produces cleaner claims.