ICD-10 codes are routinely updated and sometimes, discontinued. If one is discontinued, it will be based on date of service. For example, if you are using ICD-10 N18.3 for a patient and see on the image below that the code has been discontinued as of 10/01/2020. It will still be a valid code for dates of service 9/30/2020, but beginning on 10/01/2020 it will be invalid. To use a form of the code, you must specify an additional digit.
Within the DrChrono EHR, the ICD code search will flag discontinued codes with a "Removed since YYYY-MM-DD" message.
When you receive the "removed" or "discontinued" message, you will need to select a different, more specific code for the claim to be accepted at the payer.