ICD-10 Diagnosis Codes: Billing Basics

Use current codes

ICD-10-CM is updated on a defined schedule. Use current official coding resources for the applicable date of service rather than an old claim or static list.

Documentation supports code selection

The code should reflect the documented diagnosis or condition and the applicable coding guidelines.

Sequence and relationship matter

Claims can distinguish principal or first-listed diagnoses and additional diagnoses, and service lines can point to specific diagnoses.

Diagnosis-code review

• Use the ICD-10-CM code set and official guidelines applicable to the date of service.
• Select and sequence diagnoses from the documented clinical record rather than from an old claim.
• After changing diagnoses, recheck every claim field or service-line pointer that depends on diagnosis order.

Use the code set for the date of service

ICD-10-CM is updated over time, so a diagnosis list saved in software should never become the office’s permanent authority. Use the official files and coding guidelines that apply to the encounter date. The clinical record determines what can be coded; the claim then has to preserve diagnosis order and any links from service lines to those diagnoses. When a code is revised during coding review, recheck every downstream field that depends on the diagnosis list.

Sources and verification

Use the primary source below for the code set, identifier, security standard, or interoperability topic, and apply current payer/organizational rules to the actual workflow.

• CMS ICD-10 resources

Related guides

• CPT and HCPCS Codes: Billing Basics
• Taxonomy Codes in Medical Billing
• CARC and RARC Basics for Medical Billing