Z Codes are found in the ICD-10-CM (International Classification of Diseases, Tenth Revision, Clinical Modification) and represent reasons for encounters. Many therapists have clients who need therapy, but do not meet requirements for a diagnosis. A Z Code may be used to bill services in this situation. Z Codes, when used correctly. also eliminate billing errors, as they describe the encounter and service based off a diagnoses or lack of diagnosis, creating a clear billing record.