Substantiation means verifying that a diagnosed condition is actually active for the encounter and supported by chart documentation. The option that states validation that a given condition is active on the DOS date of service and documented reflects this precisely: the condition must be current at the time of service and backed by medical record evidence. This ensures that codes used for the encounter are accurate and justifiable, supporting proper documentation and risk adjustment. Why the other options don’t fit: a claim denial reason explains why a claim was rejected rather than whether a diagnosis is substantiated; a patient consent form is about authorization and not about diagnoses; a code set update concerns changes to codes themselves, not whether a condition is active and documented for the DOS.