When you open the ICD-10-CM Tabular List you will quickly notice notes appearing beneath many codes and categories — including two that look almost identical but mean very different things: Excludes1 and Excludes2. Misreading these notes is a common source of coding errors and CPC exam mistakes. This guide explains both types clearly with real coding examples so you never confuse them again.
Why Do Exclusion Notes Exist?
Exclusion notes exist to guide coders about conditions that are NOT classified within a particular code or category. They prevent incorrect code assignment and ensure clinical accuracy. The ICD-10-CM tabular list uses two distinct types of exclusion notes, each with a different meaning and different implications for whether two codes can be reported together.
Excludes1 — A Pure Exclusion
An Excludes1 note means the excluded condition is mutually exclusive with the code it appears under. In plain terms, the two conditions cannot occur together or be coded together at the same encounter. An Excludes1 note essentially says: “This code is never used at the same time as the code listed here.”
The reason for an Excludes1 note is usually that the excluded condition is either included in the code you are looking at, or the two conditions are clinically impossible to have simultaneously.
J06.9 — Acute upper respiratory infection, unspecified
Excludes1: acute respiratory infection NOS (J22)
This means J06.9 and J22 can NEVER be coded together for the same patient at the same encounter. They are mutually exclusive — choose one or the other.
Excludes2 — Not Included Here, But Can Be Coded Together
An Excludes2 note means the excluded condition is NOT included in the code it appears under — but the patient CAN have both conditions simultaneously and both CAN be coded together if both are documented and present. An Excludes2 note says: “This condition is not classified here, but if the patient has it, code it separately.”
The Excludes2 note is a coding guidance note — it is telling you where to find the other condition, not telling you that you cannot code both. If the patient truly has both conditions and the documentation supports it, both codes may be reported.
J45 — Asthma
Excludes2: detergent asthma (J68.0), eosinophilic asthma (J82.83), lung diseases due to external agents (J60–J70)
This means those specific types of asthma are classified elsewhere — but if a patient has both standard asthma (J45) AND a lung disease due to external agents (J60–J70), you CAN code both together.
Side-by-Side Comparison
| Feature | Excludes1 | Excludes2 |
|---|---|---|
| What it means | Pure exclusion — conditions are mutually exclusive | Not included here — but can coexist and be coded separately |
| Can both codes be reported? | NO — never at the same encounter | YES — if both conditions are documented and present |
| Clinical implication | Conditions cannot occur simultaneously OR one already includes the other | Conditions can occur simultaneously but are classified in different categories |
| Action required | Choose one code — do not report both | Code separately if both conditions exist and are documented |
| Memory tip | Excludes1 = Exclusive — only ONE | Excludes2 = Elsewhere — find the other code |
The Exception to the Excludes1 Rule
There is one important exception to the Excludes1 rule. If the Excludes1 note applies to a combination code situation — where a patient has both conditions but is using separate codes specifically for each — then both codes may be reported. This exception applies when the provider clearly documents that both separate conditions are present and neither is included in the other. This exception is rare and should be applied carefully.
Other Important Instructional Notes
While Excludes1 and Excludes2 are the most tested, the ICD-10-CM tabular list contains several other important instructional notes you should recognize:
- Includes notes: Appear at the beginning of a category and clarify what conditions ARE included in that code
- Use additional code: Instructs you to also assign another code to capture a related condition or manifestation
- Code first: Instructs you to sequence a specific underlying condition code before the current code
- Code also: Indicates that two codes may be required to fully describe the condition
- See and See also: Cross-references directing you to another index entry