This International Standard specifies requirements for certified reference materials and the content of their supporting documentation for them to be considered as higher order according to ISO 17511. It is applicable to reference materials classifiable as primary measurement standards, secondary measurement standards, [RD] and international conventional calibrators that function either as calibrators or trueness control materials. [RD What about precision control materials, cf. 4.5]This International Standard also provides requirements on how data shall be collected for value determination and how to present the assigned value and its measurement uncertainty. This International Standard applies to reference materials with assigned values of differential or rational quantities. For nominal properties and ordinal quantities, see Annex A. This International Standard does not apply to reference materials that are parts of an in vitro diagnostic measuring system, although many elements may be helpful.