This document gives general information on the key steps for the preparation of candidate matrix reference materials (RMs) including the material specification, sourcing and selection of bulk material, and the processing of the material, which are important steps for the production of matrix RMs. The document provides information on the preparation of candidate RMs for laboratory staff who prepare and use matrix materials for their specific applications. This document can also be used by reference material producers (RMPs) as an information source for the preparation of the RMs that they produce. This document also offers examples of specific case studies covering the preparation of matrix RMs in different fields of application (see Annexes A to F). These are not complete "production manuals" but highlight key considerations for the preparation steps of RMs.