Self-assessment obligations: correct classification and transaction based valuation determine excise duty liability at removal. Assessment requires assessees to self determine classification, applicable rate and assessable value at removal; transaction value applies where sales are at arm's length with price as sole consideration, otherwise Valuation Rules prescribe alternatives including additions for additional consideration, special rules for related party and depot sales, and cost based valuation for captive consumption. Provisional assessment requires written request, departmental order specifying provisional rate/value and security, mandatory finalisation within prescribed limits and monitoring; duty payment is by Personal Ledger Account or CENVAT credit with defined procedures for deposits and delayed payment consequences.