This International Document sets out guidelines for the development of legal requirements applicable to certified reference materials (CRMs) used in the framework of metrological activities covered, in conformity with national laws, by the metrological control and supervision exercised by national services of legal metrology. Note: National laws may specify the fields of activity in which the metrological control and supervision of measuring instruments, standards, measurement procedures, etc., shall be exercised by the bodies of the national metrological service or other authorized organizations [A.l]. In this International Document, the abbreviation SMCS is used to refer to the state metrological control and supervision that cover such fields. It is recommended that the principles set out in this International Document be implemented in the development of OIML publications and in the activities of national legal metrology services. This International Document has been developed taking into consideration the general concepts expressed in ISO/REMCO and OIML publications concerning the use of CRMs as standards in metrological activities. Account has also been taken of concepts set out in other OIML publications establishing general metrological requirements and rules such as the competence of legal metrology services, the fields covered by state metrological control [A.l], legal requirements and type approval procedures [A.2], the principles of establishing standards and traceability [A.3, A.4], etc. This International Document is also based on ISO/REMCO Guides 30 to 35 (see Annex A) and supplements these Guides with a view to facilitating a wider use of reference materials in SMCS.