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HMRC internal manual

Guidance on the Audit of Customs Values

Exclusions from the customs value: contingency discounts

A seller normally grants these when the buyer has purchased a large quantity over a given period.

The discount relates to all importations in the period and not to one importation.

A contingency discount is not allowable where it is claimed in full on one importation. It must be applied to the importations to which it relates (WCO AO 8.1 and 15.1 also refers).