Question Discharge date clarification

Coquille, OR
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I have been working with our coding software company about the effective dates of new ICD10 codes in October of each year. They are telling me that the effective date for inpatients is the discharge date. However, they are stating they are using the admit date for outpatients. I feel it should also be the discharge date, as CMS states for "discharges". I have an outpatient claim that spans from a September date and discharges on an October date. I am just putting this out to get anyone's input on this. If this is correct and it is discharge dates for inpatient and outpatient, would anyone have anything in writing that I could use? Thank you in advance.