Medicare Billing Mistakes Doctors Should Avoid in 2026

Medicare billing can become complicated quickly, especially when a practice handles multiple provider types, specialties, procedures, modifiers, and payer requirements. A small mistake in documentation, coding, claim submission, or provider information can delay payment or result in a denial.

For physicians, the problem often starts before the claim reaches Medicare. A provider may document a service correctly but use the wrong code. A biller may submit the right CPT code with the wrong modifier. A practice may treat a Medicare Advantage claim like an Original Medicare claim. Another claim may go unpaid because nobody followed up before the payer’s filing deadline.

These problems can add up.

The good news is that most Medicare billing mistakes follow recognizable patterns. Once your practice identifies those patterns, you can build workflows that prevent them.

Let’s discuss the most common Medicare billing mistakes doctors should avoid, along with practical steps for improving claim accuracy, documentation, reimbursement, and compliance.

Medicare Billing Mistakes and Their Solutions 

Medicare billing rules vary by service, provider type, place of service, Medicare program, and date of service. Always verify current CMS guidance, the Medicare Administrative Contractor’s requirements, NCDs, LCDs, National Correct Coding Initiative edits, and applicable payer policies before submitting claims.

Coding a Service That the Documentation Does Not Support

One of the most serious Medicare billing mistakes involves selecting a code that the medical record does not support.

Physicians should never choose a CPT code simply because it produces higher reimbursement.

The documentation must support the service reported on the claim.

For evaluation and management services, Medicare generally bases office or other outpatient E/M code selection on medical decision making or total time on the date of service, depending on the code family and documentation requirements.

For example, a physician should not select a higher-level E/M code simply because the patient has multiple diagnoses.

The record should support the reported service.

How to prevent it

Create a clear connection between:

• Clinical work → Documentation → CPT code → Claim
• Physicians should document the actual work performed rather than writing notes specifically to justify a predetermined code.

Upcoding Evaluation and Management Services

Upcoding occurs when a practice reports a higher level of service than the documentation supports.

This can happen intentionally or accidentally.

For example, a physician might routinely report a high-level established patient E/M code for nearly every follow up visit.

That pattern can attract payer scrutiny if the documentation does not support the reported services.

Medicare also uses claims data and other information to identify unusual billing patterns.

What doctors should do

• For each E/M service, make sure the record supports the selected level through the applicable coding methodology.
• For MDM based coding, document the problems addressed, data reviewed and analyzed, and risk of patient management as required by the current CPT framework.
• For time-based reporting, document the total time when the applicable code permits selection based on time and make sure the documented time meets the code’s requirement.

Using the Wrong ICD 10 Diagnosis Code

Medicare requires diagnosis coding that accurately represents the patient’s conditions and supports the services reported.

A diagnosis code should not appear on a claim simply because it appears somewhere in the patient’s historical problem list.

For example, a patient may have a history of hypertension, diabetes, and hyperlipidemia.

If the physician only addresses hypertension during a particular encounter, the practice should not automatically assume that every chronic diagnosis belongs on the claim.

The medical record should support the diagnoses reported.

Common diagnosis coding problems

• Using an unspecified code when documentation supports greater specificity. 
• Reporting historical conditions as active conditions. 
• Using outdated codes. 
• Reporting diagnoses that the physician did not address when the payer requires a connection to the service. 
• Choosing a diagnosis that does not support medical necessity for the service. 

Best practice

Coders should review the actual documentation rather than relying on the patient’s existing diagnosis list.

Choosing the Wrong Modifier

Modifiers can significantly affect Medicare payment.

A modifier tells Medicare that a service differs in some specific way from the standard circumstances described by the CPT code.

Common examples include:

• Modifier 25, for a significant, separately identifiable E/M service on the same day as another procedure or service when the applicable requirements are met. 
• Modifier 59, used to identify a distinct procedural service when appropriate. 
• Modifier 24, for an unrelated E/M service during a postoperative period when the applicable requirements are met. 
• Modifier 26, for the professional component of certain services. 
• Modifier TC, for the technical component of certain services. 

The mistake occurs when staff use a modifier as a payment shortcut.

For example, adding modifier 25 to every office visit performed on a procedure day does not automatically make the E/M service separately payable.

The documentation must support the modifier.

Ignoring NCCI Edits

The National Correct Coding Initiative (NCCI) helps prevent improper payment when certain procedure code combinations should not normally receive separate payment.

• Practices should review applicable NCCI edits before submitting claims containing multiple procedures.
• If an edit permits a modifier override, the practice should verify that the clinical circumstances genuinely support that modifier.
• Do not override an edit simply because the claim denies without the modifier.

The modifier must describe what actually happened.

Billing the Wrong Place of Service

Place of Service codes tell Medicare where the service occurred.

Examples include:

• Office. 
• Inpatient hospital. 
• Outpatient hospital. 
• Emergency department. 
• Nursing facility. 
• Home. 
• Telehealth related settings, where applicable. 

Using the wrong POS code can affect reimbursement and claim processing.

For example, a physician may see a patient in an outpatient hospital department but accidentally submit the claim with an office POS code.

That mismatch can trigger an incorrect payment or denial.

Best practice

Make sure the EHR, scheduling system, charge capture process, and billing system use the same location information.

Confusing Original Medicare with Medicare Advantage

This mistake can create significant claim problems.

Original Medicare and Medicare Advantage do not follow exactly the same billing workflow.

Original Medicare claims generally go through Medicare’s claims processing system and the applicable Medicare Administrative Contractor.

Medicare Advantage claims go to the patient’s Medicare Advantage organization according to the plan’s requirements.

• A practice should verify the patient’s actual coverage before submitting the claim.
• Do not assume that every patient with a Medicare card receives services under Original Medicare.

Failing to Verify Medicare Eligibility

Eligibility verification can prevent avoidable billing problems.

Before services occur, staff should confirm applicable coverage and identify whether the patient has:

• Original Medicare. 
• Medicare Advantage. 
• A Medicare Supplement policy. 
• Medicaid. 
• Another primary payer. 
• Employer coverage. 
• Other insurance. 

Coordination of benefits becomes especially important when another payer may have primary responsibility.

Using the Wrong NPI

A National Provider Identifier identifies healthcare providers for HIPAA standard transactions.

But an NPI does not prove:

• Licensure. 
• Credentialing. 
• Medicare enrollment. 
• Assignment status. 
• Payer participation. 

Practices must submit provider information that accurately reflects the claim and the applicable Medicare enrollment arrangement.

Using the wrong billing or rendering provider information can result in claim rejection, denial, or payment problems.

Ignoring Incident to Requirements

Incident to billing creates another common source of Medicare errors.

Medicare allows certain services furnished by auxiliary personnel to qualify as incident to when specific requirements are satisfied.

Those requirements can involve:

• An established patient relationship. 
• An established treatment plan. 
• The supervising practitioner’s continuing involvement. 
• Required supervision. 
• Appropriate employment or contractual arrangements. 
• Covered services. 
• Applicable Medicare rules. 

Simply having a physician in the building does not automatically make every service incident to.

Practices should maintain a written incident to policy and train both clinical and billing staff.

Missing Medical Necessity Requirements

Medicare generally pays only for covered services that meet applicable medical necessity requirements.

A claim can contain the correct CPT code and still fail because the documentation does not establish why the service was medically necessary.

This issue frequently appears with:

• Diagnostic testing. 
• Imaging. 
• Procedures. 
• DME. 
• Certain injections. 
• Specialty services. 

Before billing, the practice should confirm that the diagnosis and documentation support the service under the applicable Medicare coverage policy.

Ignoring NCDs and LCDs

Medicare coverage policies can provide important guidance.

A National Coverage Determination (NCD) applies nationally when CMS issues one for a service.

A Local Coverage Determination (LCD) may apply within a Medicare Administrative Contractor’s jurisdiction.

Practices should review applicable coverage policies when billing services subject to specific coverage requirements.

These policies can address:

• Covered indications. 
• Diagnosis requirements. 
• Frequency limits. 
• Documentation. 
• Medical necessity. 
• Noncovered circumstances. 

A billing team should not rely solely on a general coding reference when a service has a specific Medicare coverage policy.

Missing Timely Filing Deadlines

Medicare has specific claim submission deadlines.

For many Original Medicare claims, providers generally must submit claims no later than 12 months after the date of service.

That does not mean practices should wait.

The longer a claim remains unsubmitted, the greater the risk of:

• Missing documentation. 
• Lost claim information. 
• Eligibility changes. 
• Filing deadline problems. 
• Difficult A/R recovery. 

Submit clean claims as soon as reasonably possible.

Failing to Track Medicare Denial Trends

A practice that only looks at total denied dollars misses valuable information.

Track denials by:

• CPT code. 
• ICD 10 code. 
• Provider. 
• Location. 
• Medicare contractor. 
• Denial reason. 
• Modifier. 
• Date of service. 
• Dollar amount. 

Suppose 40% of your Medicare denials involve modifier 25.

That points to a workflow problem.

The solution may involve provider education, coding review, or documentation changes.

Failing to Understand Medicare Deductibles and Coinsurance

Patient responsibility can affect claim posting and collection.

The practice should correctly process Medicare payments and determine applicable patient responsibility based on the patient’s coverage.

For patients with secondary coverage, staff should also understand coordination of benefits.

Incorrectly assigning patient responsibility can lead to:

• Patient complaints. 
• Incorrect statements. 
• Delayed collections. 
• Refunds. 
• Rework. 

A Medicare Billing Checklist for Physicians

Before submitting a Medicare claim, your practice should be able to answer these questions:

Patient

• Does the patient have active Medicare coverage? 
• Does Original Medicare or a Medicare Advantage plan apply? 
• Does another payer have primary responsibility? 

Documentation

• Does the medical record support the service? 
• Does it establish medical necessity? 
• Did the physician document the actual work performed? 
• Does the documentation support the selected code? 

Coding

• Is the CPT or HCPCS code correct? 
• Is the ICD 10 diagnosis code accurate? 
• Does the diagnosis support medical necessity? 
• Are modifiers appropriate? 
• Did the claim pass applicable NCCI edits? 

Provider

• Is the correct rendering provider reported? 
• Is the billing provider correct? 
• Does the billing arrangement comply with Medicare requirements? 

Claim

• Is the place of service accurate? 
• Are required claim fields complete? 
• Has the claim met timely filing requirements? 

After Submission

• Did Medicare accept the claim? 
• Did Medicare pay correctly? 
• If denied, did the team identify and correct the actual problem? 
• Does the payment match the expected reimbursement? 

Final Takeaway

Medicare billing mistakes rarely come from one complicated rule.

They usually come from small disconnects between documentation, coding, claim submission, payer requirements, and follow up.

The most important step involves creating a process where every claim tells the same story:

• The physician performed the service.
• The medical record supports the service.
• The diagnosis supports medical necessity.
• The coding accurately represents the service.
• The claim identifies the correct provider and payer information.
• The practice follows the applicable Medicare rules.

When those pieces align, practices can reduce avoidable denials, improve reimbursement accuracy, and spend less time correcting preventable billing problems.