Coding errors and their link to denials
Incorrect or incomplete coding is a frequent driver of preventable denials and underpayments. Common issues include:
- Diagnosis codes that do not support the procedure
- Missing or incorrect modifiers (especially for global periods, assistants, or bilateral procedures)
- Upcoding or undercoding relative to documentation
- Failure to capture all billable elements of a multi-procedure encounter
- Use of outdated codes after annual CPT or ICD-10 updates
These errors are often correctable when caught before submission. Once denied, correction requires additional staff time and may still fail if the underlying documentation is insufficient.
Biller versus coder roles
A medical coder assigns the procedure and diagnosis codes based on clinical documentation and official guidelines. A medical biller typically manages claim submission, payment posting, denial follow-up, and patient billing. In smaller practices the roles may overlap; in larger settings they are often separated so that coding quality can be reviewed independently of billing production.
Both roles require current knowledge of payer-specific rules. Neither role replaces clinical documentation responsibility, which remains with the treating provider.
Compliance considerations
Billing compliance risk increases when:
- Documentation does not support the codes submitted
- Claims are submitted without required authorizations or eligibility confirmation
- Workqueues lack clear ownership or audit trails
- Software edits are overridden without documented rationale
Regular sample audits, documented escalation for unclear cases, and current code-set updates reduce exposure. Practices should also monitor for patterns that could trigger payer or government review.
Common mistakes that cost practices money
- Submitting claims with placeholder or incomplete data
- Ignoring clearinghouse rejections
- Failing to reconcile expected versus actual payment
- Letting aged balances age further without triage
- Treating every unpaid claim the same way regardless of viability
Related resources
- Preventing Upcoding and Undercoding Audits
- CPT Code Updates and ICD-10 Scrubbing
- Medical Billing Services
References
- CMS ICD-10 and CPT resources
- AMA CPT resources (official code set)
Editorial note: October 12, 2026. Coding and compliance requirements change. Confirm current guidelines and payer policies before use.