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HMRC internal manual

Customs Special Procedures Manual

General relief conditions: rate of yield

This term is used to express the quantity of processed product obtained from a unit quantity of imported goods. The rate of yield should be specified on the application, and verified by post authorisation checking of the processing records. It is important that the rate of yield is accurate. If too low, the authorisation holder could be fraudulently diverting goods to an ineligible use.

Where more than one product is obtained from the approved processing operations, you must establish a rate of yield for each distinguishable and marketable product. Where goods are used up during processing, for example, by loss through evaporation, desiccation, venting as gas or leeching, these production losses should be subtracted from the quantity of import goods prior to establishing the rate of yield.