This document describes the framework for building a system for classification of requirements. Such a system can be used to indicate requirements of special importance, and communicate them for production set-up, verification, and audit etc. This document gives background information why such a system is useful in many areas of manufacturing; can be referred to for the concept of classification of requirements; functions as a framework for applying such a system in technical product documentation (TPD); indicates the needed elements for a classification system; supports with aspects in the choice of symbols for a classification system. As a framework this document does not give the details of a specific classification system. Instead, it functions as a basis for an organization specific system which contains the details such as notations and symbols, classification levels, assessment procedures etc., including usage and interpretation in the TPD. This document does not describe contractual consequences of a classification e.g., required actions like choice of tools, reliability index or process capability for a classification level, nor needed references to other such standards or documents for handling classifications and non-conformity to requirements.