Inpatient coding refers to a diagnosis report for patients who require hospitalization and must be admitted for an extended stay. Inpatient coding uses Internal Classification of Diseases, Tenth Revision (ICD-10) coding systems. Outpatient coding refers to reports outlining services for patients who aren’t required to be hospitalized, typically those who are released within 24 hours. Outpatient coding uses Current Procedural Terminology (CPT) coding systems. Inpatient and outpatient coding also deal with unique payment and reimbursement systems you will need to be familiar with. You may learn inpatient and/or outpatient coding depending on whether you choose the associate degree or diploma path.