Ref: https://chat.fhir.org/#narrow/stream/197730-Da-Vinci.20PDex.20Drug.20Formulary/topic/Mail.20Order.20Question

"We’re currently mapping a formulary to Coverage Plan (List) and FormularyDrug (MedicationKnowledge). The CoveragePlan profile has the mail order indicator (Yes/No) and it appears to be required under the usdf-DrugTierDefinition-extension. However, mail order is not a “plan-level” attribute. It is an attribute of the drug. e.g. I’m on Medicare Advantage plan and I can get Atorvastatin through mail order but I can’t get Adempas via mail order. Both drugs are in the same formulary. Has anyone come across this issue and, if so, how did you handle it?"

The current IG (based directly on the QHP formulary) only allows specification of mail order at the plan-level, as you noted. There is no facility to identify FormularyDrugs that do (not) have mail order options.