Prevent medical coding mistakes and reduce claim denials

Why coding errors are a workflow problem, not a people problem

A denied claim rarely starts with a single mistake. More often, it's the result of a workflow gap — unclear documentation or a missing modifier that triggers rejection. By the time the denial arrives, your practice is already behind. Revenue is delayed, staff time is spent on rework, and preventable errors compound.

For practices managing medical coding with lean teams, these challenges compound quickly. Many common medical coding mistakes follow predictable patterns. They likely happen at the same pressure points in your workflow, for the same underlying reasons.

With the right processes and system support, these errors are preventable.

The most common medical coding mistakes practices face

Medical coding errors fall into recognizable patterns. Understanding why they happen is the first step toward reducing claim denials. Here are some of the most frequent culprits:

Unbundling and upcoding

Unbundling occurs when a procedure that should be billed with a single code gets split into multiple component codes.¹

Upcoding happens when the service billed doesn't match the complexity of care delivered.²

Modifier misuse and omissions

Modifiers communicate critical details about how and where a service was performed, but they're a frequent source of errors. Laterality mistakes — failing to indicate which side of the body was treated — can trigger immediate denials. Reporting modifier 50 (bilateral procedure) to a procedure code that already includes bilateral service results in duplicate payment requests that payers will reject.³

Overusing modifier 22 (increased procedural services) is also problematic. This modifier requires documentation to explain why the procedure requires more work than usual — such as a lesion excision made more complex by a patient's obesity. Without adequate supporting documentation, using modifier 22 creates payer scrutiny and delays.⁴

NCCI edit violations

The National Correct Coding Initiative (NCCI) maintains automated rules about which code combinations can and can't be billed together for the same patient on the same date. When your claim includes an incompatible pairing, the payer's system automatically flags it.

By the time the denial comes back, the claim needs to be researched, corrected, and resubmitted — adding weeks to your payment timeline.⁵

Time-based coding documentation gaps

For services like infusions and hydration that are billed based on time, accurate start and stop times are essential. When documentation happens separately from coding, or when it's rushed, these details get missed or recorded inconsistently.⁶

Demographic and patient data errors

While not technically coding errors, mistakes like capturing incorrect insurance information, patient demographics, and eligibility details are among the most common causes of claim rejection. According to Optum's 2024 Revenue Cycle Denials Index registration and eligibility errors account for 24% of all denials, making them the single largest denial category.⁷

Critical insight: 84% of denials are potentially avoidable, yet 50% are nonrecoverable — meaning they represent permanent revenue loss.⁸

Why these errors happen: The workflow gap

Coding and billing errors are outcomes of workflow designs. Three critical gaps drive preventable errors:

#1. Clinicians coding their own work under time pressure

Some practices may rely on clinicians to select codes immediately after patient encounters, often with limited coder review. When a provider is running behind schedule, there’s pressure to select codes quickly and move on. This creates an environment where subtle distinctions between code categories get overlooked, modifiers are missed, and documentation shortcuts become routine.

#2. Documentation occurring separately from coding

Clinical documentation and coding often happen in silos, creating information gaps that directly contribute to errors. A physician documents a patient encounter in the EHR, focusing on clinical details. Days later, a coder reviews that documentation to assign billing codes.

According to Optum's 2024 Revenue Cycle Denials Index, missing or invalid claim data accounts for 16% of all denials, the second-largest category after registration issues.⁹ When documentation doesn't support the codes submitted, payers reject the claims.

#3. Volume pressures during peak periods

Healthcare isn't a steady-state operation. Practices experience surges during flu season, end-of-year insurance rushes, and post-holiday catch-ups. During these high-volume periods, the pressure to process claims quickly intensifies. Staff who might normally catch errors must prioritize speed over accuracy.

Specialty-specific pitfalls

While coding challenges affect all practices, certain specialties face particularly high-risk scenarios where small errors can trigger significant denials.

Oncology: Complex E/M coding and infusion time documentation

Oncology practices juggle some of the most complex coding scenarios in healthcare. Chemotherapy administration codes require precise documentation of infusion start and stop times, push versus infusion methods, and whether drugs are given at the same time or one after another. A missing time stamp can result in claim denials or downcoding that costs thousands of dollars per treatment session.

E/M (Evaluation and Management) coding in oncology is equally challenging. Cancer patients often require high-level services, but without documentation that addresses the complexity of medical decision-making, payers may downcode to lower-level visits.

Orthopedics: Laterality and modifier 50 on bilateral procedures

Orthopedic practices face frequent denials related to laterality and bilateral procedure coding. Every procedure code must specify left, right, or bilateral using the appropriate modifier. Missing or incorrect laterality modifiers trigger immediate denials, even when the procedure itself is correctly coded and medically necessary.

Modifier 50 (bilateral procedure) presents another common pitfall. Some payers require modifier 50 for bilateral procedures, while others want the same code listed twice with RT (right) and LT (left) modifiers. When practices don't verify payer-specific billing requirements, claims are denied.

Primary Care: E/M level selection and preventive versus diagnostic visits

Primary care practices must correctly distinguish between preventive and diagnostic visits — a distinction that significantly impacts reimbursement. When a patient schedules a routine physical but raises new symptoms during the visit, the encounter may require both a preventive code and a problem-oriented E/M code with modifier 25. Missing this modifier results in the diagnostic portion being denied as a duplicate service.

E/M level selection remains the most frequent coding challenge in primary care. The 2021 E/M guidelines simplified documentation requirements,¹⁰ but many practices still struggle to consistently capture the medical decision-making complexity that supports higher-level codes.

The Real Cost of Coding Errors

Coding errors don’t just impact the bottom line — they create operational drag across your practice.

The average claim denial costs practices up to $64 to rework, depending on complexity and payer type.¹¹  For a mid-sized practice processing 500 claims monthly with a 10% denial rate (50 denials/month × 64/denial × 12 months), that translates to approximately $38,400 in annual denial management costs — not counting the original lost revenue and potential write-offs.

Building better workflows to prevent errors

Reducing coding errors means building systems that catch mistakes before claims leave your practice. The most effective approach combines process improvements, technology tools, and system-level support that work together to prevent errors rather than just catch them.

Start by catching errors early with pre-submission claim validation and real-time coding guidance. Specialty-specific templates prompt clinicians for critical details like which side of the body was treated, timestamps, and modifiers right at the point of care — not days later when details fade.

Technology amplifies these practices by integrating EHR and billing workflows, which reduces the back-and-forth between clinical and revenue cycle teams. Built-in NCCI edit checking flags incompatible code combinations before submission. Automated demographic and eligibility verification runs at scheduling and check-in. Claims scrubbing identifies missing modifiers, documentation gaps, and billing errors before payers see them.

System-level support provides visibility to help you identify patterns and address root causes. Denial pattern analysis reveals which codes, payers, or workflows generate the most rejections — so you can fix systemic issues, not just individual claims.

athenaOne® connects clinical documentation, coding, billing, and collections in a single system — reducing the handoffs that create errors. Real-time coding guidance prompts clinicians and billing staff at the point of service. Automated claims scrubbing reviews every claim before submission, catching NCCI violations, modifier omissions, and documentation gaps. Because athenahealth processes claims for thousands of practices, the platform continuously updates coding rules and payer requirements — so your team doesn't have to track every change manually.

On average across the athenahealth network, athenaOne Medical Coding Services has delivered 99.4% coding accuracy, outperforming the industry standard of 95%.¹² The network has also seen a 30% increase in payment recovery for coding-related denials when practices use AI-powered denials advice versus manual rework alone.¹³ Individual results may vary.*

Moving forward: From reactive to proactive

Reducing coding errors is about building systems that catch issues before they become denials. Because most coding errors stem from structural problems in workflows, the solution is to redesign workflows, implement real-time guidance, and catch errors at the source.

Ready to reduce coding errors and speed up claims processing? athenaOne Medical Coding Services deliver fast, accurate coding from certified specialists — integrated directly into your workflow to eliminate backlogs and improve accuracy.