7 Common Medical Billing and Coding Errors (And How to Solve Them)

A claim returns unpaid. Your team corrects it, submits it again, and moves on. But if the original problem remains in registration, documentation, or a billing-system rule, the next claim can repeat it.

Preventing medical billing and coding errors requires more than checking codes. Your team needs to identify where information went wrong, correct affected claims, and fix the workflow responsible.

This guide covers seven recurring errors for U.S. physician and outpatient practices. Medicare examples are identified; requirements differ by payer and setting.

Medical Billing and Coding Errors (How to Prevent Them)

1. Incorrect Patient Information or Unverified Coverage

Wrong member IDs, outdated insurance details, and incorrect payer order can disrupt an otherwise accurate claim.

Example: A returning patient changes insurers, but the claim uses the previous plan.

Prevent it: Verify patient and subscriber details, coverage dates, primary payer, and applicable referral or authorization requirements. Save verification references. Active coverage alone does not establish that every service is payable. CMS provides eligibility transactions and coordination-of-benefits guidance to support these checks.

Correct it: Update the source record and follow the payer’s correction process. Check other unsubmitted claims affected by the same mistake.

Owner: Registration/eligibility staff, with billing handling claim corrections.

2. Documentation That Does Not Support the Claim

A valid code does not resolve missing clinical information. Errors also occur when a billed service links to an unrelated diagnosis on the claim.

Example: A test points to an old diagnosis instead of the documented reason for ordering it.

Prevent it: Check the service, clinical reason, required orders, signatures, and diagnosis linkage. Ask the clinician to clarify missing information; never invent details or change diagnoses to secure payment. Check applicable coverage policies.

Correct it: Compare the claim, record, and payer response. Preserve the audit trail when amending documentation, then use the appropriate correction or appeal route.

Owner: Clinician and coder.

3. Incorrect or Outdated Codes

Codes may be invalid for the service date, incomplete, or inconsistent with the record. Templates and favorites can preserve outdated selections even after software updates.

Example: A template supplies an unspecified-side diagnosis although the affected side is documented.

Prevent it: Check code validity, required characters, laterality, and sequencing. Use documented specificity; unspecified codes can be appropriate. For outpatient services, do not code suspected or rule-out diagnoses as confirmed.

2026 update: FY 2027 ICD-10-CM took effect October 1, 2026. Use the release applicable to the encounter or inpatient discharge date. HCPCS Level II files and NCCI edits also require attention throughout the year.

Correct it: Fix supported coding errors and affected templates; identify other impacted claims.

Owner: Coding lead and system administrator.

4. Upcoding or Downcoding

Upcoding reports a higher service level than warranted; downcoding reports a lower level than supported.

Example: An office-visit level follows scheduled appointment length rather than documented medical decision-making or qualifying practitioner time.

Prevent it: Apply the relevant evaluation and management family’s rules. Most E/M visit families use medical decision-making or practitioner time; some require a particular method. A longer note alone does not justify a higher level.

Correct it: Review the encounter and follow applicable claim-correction and overpayment procedures. Escalate concerning patterns to compliance. An incorrect code is not automatically proof of fraud.

Owner: Coding reviewer and treating clinician.

5. Incorrect Modifiers or Place-of-Service Codes

Modifiers communicate qualifying circumstances; place-of-service codes identify the setting. Neither should come from an unchecked default.

Example: A billing rule automatically adds modifier 59 whenever an edit appears.

Prevent it: Validate circumstances and documentation. For Medicare, modifier 59 is not a general denial override; use a more descriptive modifier when appropriate. Modifier 25 requires a significant, separately identifiable E/M service beyond usual procedural care.

For Medicare physician/practitioner telehealth billing, POS 10 identifies the patient’s home; POS 02 identifies another location. Verify modality, service eligibility, and modifier requirements separately.

Correct it: Review the encounter before changing codes, and repair unsupported defaults.

Owner: Coder, with system-administrator support.

6. Unbundling Services or Reporting Incorrect Units

Unbundling separately reports components included in a comprehensive service. Incorrect units misstate the quantity billed.

Example: An interface imports duplicate units, or staff enter the administered quantity without checking the code’s billing unit.

Prevent it: Review applicable Procedure-to-Procedure edits for code combinations and Medically Unlikely Edits for quantities. Reconcile units with the descriptor and record.

For Medicare NCCI, modifier indicator “1” permits exceptions only when qualifying circumstances support them. Indicator “0” does not allow a modifier override.

Correct it: Reconcile charges, make appropriate adjustments, and check whether interface defects affected other accounts.

Owner: Coding and charge-entry teams.

7. Duplicate Charges or Claims

Duplicate billing can result from repeated charge entries or resubmitting an original claim while it is processing.

Example: One biller resubmits a claim another employee is already monitoring.

Prevent it: Check acknowledgments and claim status first. CMS specifically advises against resubmitting Medicare claims during front-end editing because this creates duplicates. Maintain one follow-up owner per account.

Correct it: Identify the valid charge or claim before canceling anything. Follow applicable procedures for duplicate payments. A genuinely repeated service requires appropriate reporting, not automatic deletion.

Owner: Billing follow-up team.

How to Resolve an Unpaid Claim

Read the actual response before deciding what to do:

A denial does not prove the coding was wrong. 

Medicare distinguishes minor-error corrections from appeals. Track filing and appeal deadlines separately; a reopening request does not pause Medicare appeal deadlines.

Your Pre-Submission Checklist

Confirm identifiers, coverage, documentation, code validity, service levels, modifiers, POS, units, bundling, duplicates, and filing deadlines. Medicare generally requires filing within 12 months of service, subject to exceptions; other payers vary.

Software should flag issues for review; it cannot supply missing clinical facts. When corrections change patient responsibility, review affected statements.

Track first-submission rejections, initial denials, and repeat errors separately. Define denominators consistently and separate claim-level from line-level measures. Assign recurring problems to the team that can fix their source.

Start with a small sample of recent problem claims. Record the original error, its source, the correction, and whether the payer accepted the next action. Use the findings for targeted training rather than asking everyone to repeat a general coding course.

When evaluating software or an outside billing partner, ask how updates are tested, documentation questions reach clinicians, and unresolved claims remain visible. 

A useful process should show who owns each exception and what happens next, with documented follow-up rather than an unexplained claim status.

Need Help With Recurring Billing Errors?

If documentation gaps, coding edits, or duplicate submissions keep returning, CapMinds can help review your billing and coding workflow and discuss appropriate support.

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