Classification of excisable goods determines duty rates, with specific headings and exemptions shaping the effective liability. Levy of central excise duty depends on placement of goods within the Central Excise Tariff, with Classification determining the applicable heading and tariff rate; specific headings prevail over general ones. Duty is payable at prescribed tariff rates subject to exemption Notifications that modify the effective rate. For ad valorem duties, Valuation typically uses the transaction value where price is sole consideration between unrelated parties, otherwise valuation follows prescribed rules; alternative assessments apply where MRP-based assessment under Section 4A or tariff value under Section 3(2) is notified.