GST assessment on transaction value ensures end to end input tax credit neutrality across drug supply chains. Assessment of drugs and formulations under GST is on the basis of transaction value at each level of supply with an end to end ITC chain to neutralise GST paid at procurement. Physician samples free of cost require reversal of ITC under Section 17(5)(h) and attract no tax where value is zero and no credit was availed. Transitional credits and movement/destruction of expired goods follow specified provisions and time limits under Sections 34, 140 and Rule 117.