Excise is charged on units or on value depending on the product, and the choice decides how the duty is computed. Constant-volume products such as spirits and tobacco are commonly charged per unit, while others follow the value route, where the excise arises on the transaction price of the dutiable goods at the point of removal from the plant. When value is the base, the figure is the normal price of the goods at clearance to the market, the genuine arm's length value before distribution margins are added by intermediaries. The valuation problem appears when related parties trade: sales to connected distributors can carry thin prices unless the assessment holds the full value of the equivalent open-market sale. The audit trail therefore runs through the wholesale price. A manufacturer who packs value through captive distributors and claims a low excise base invites adjustment to the open-market level of its own product. Making the distributor margin demonstrable and the removal price consistent, with the pricing documents in the file, keeps the assessment on the number that production genuinely earned and the department recognises.