A method of identifying a product comprises forming a tagged product by adding to said product a tracer material comprising at least one tracer compound which is acceptable for use as an additive in food and subsequently analysing a sample of said product to determine the presence of said tracer compound thereby to determine whether said sample is a sample of the tagged product. The method is especially useful for the identification of vegetable oil products from sustainably managed sources. The use of permitted food additives as tracers enables the product to be identified in the supply chain whilst also allowing it to be used safely in foodstuffs if required.