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HMRC internal manual

Customs Special Procedures Manual

Production accessories: rate of yield

Although catalysts are not found in the processed products, a rate of yield for the catalyst used during processing must be established so that duty liability on the catalyst used to produce each processed product can be accounted for.

An example calculation can be found in Notice 3001/2015, Annex D.

If any used catalyst is left over, refer to SPE13455 and SPE13460 of this guidance.

Notice 3001/2015, Annex D Section 4.6