What is ISO/IEC/IEEE 15026-4 about?  
 ISO/IEC/IEEE 15026-4 is the fourth part of a series of documents applicable to system and software assurance. ISO/IEC/IEEE 15026-4 provides guidance and recommendations for the assurance of a selected claim about the system of interest by achieving the claim and showing the achievement.
The guidance and recommendations are given in a system assurance process view on top of ISO/IEC/IEEE 15288 and a software assurance process view on top of ISO/IEC/IEEE 12207.
ISO/IEC 150262, ISO/IEC 150263 and ISO/IEC/IEEE 15026-4 all use the concepts and vocabulary defined in ISO/IEC/IEEE 150261; however, any part may be applied independently of the others and the use of one does not require the use of any others. 
The conformance to ISO/IEC/IEEE 15026-4 shall be achieved in either or both of the following ways:
- Achieving the required outcomes of the system assurance process view, in addition to conforming to ISO/IEC/IEEE 15288
- Achieving the required outcomes of the software assurance process view, in addition to conforming to ISO/IEC/IEEE 12207
Who is ISO/IEC/IEEE 15026-4 for? 
ISO/IEC/IEEE 15026-4 on systems and software assurances is useful for: 
- Software engineers
- Software project managers
- Software testers
- System engineers
- Authoritative bodies for regulation
Why should you use ISO/IEC/IEEE 15026-4?  
 ISO/IEC 150262 provides minimum requirements for the structure and contents of assurance cases that treat claims regarding properties of a system or software product selected for special treatment. The results of performing the life cycle activities and tasks referenced in ISO/IEC 150262 can be recorded in the form of the assurance.
Using ISO/IEC 150262 software engineers can improve the quality of the software. ISO/IEC/IEEE 15026-4 can be used for establishing an agreement between an acquirer and a supplier, for regulatory purposes, or for the assessment of internal development processes. ISO/IEC/IEEE 15026-4 clarifies what it means both to achieve the assurance claim and to demonstrate that the assurance claim is achieved. ISO/IEC/IEEE 15026-4 can be used for establishing an agreement between an acquirer and a supplier concerning achieving the assurance claim and showing the achievement.
What’s changed since the last update? 
ISO/IEC/IEEE 15026-4:2021 supersedes BS ISO/IEC 150264:2012, which is withdrawn.
 The main changes compared to the previous edition are as follows:
- References to the life cycle processes standards (ISO/IEC 15288:2008 and ISO/IEC 12207:2008, respectively) are changed to refer to their updated versions (ISO/IEC/IEEE 15288:2015 and ISO/IEC/IEEE 12207:2017, respectively)
- Outcomes of the process views are changed to make the link to their purpose clearer
