ISO 27001 and ISO 20000

Answer: I'm assuming you are asking if ISO 27001 certified organizations also needs to certify on ISO 20000. Considering that, I can say to you that being ISO 27001 certified does not ensure you are compliant with all requirements of ISO 20000 (ISO 27001 covers information security, while ISO 20000 covers IT services), so if an organization decides, or is required, to operate an IT service management system, it will need to work with ISO 20000 also, but as I said before, the effort will be lesser, because some requirements are already covered by ISO 27001 certified system.

These articles will provide you further explanation about ISO 27001 and ISO 20000:
- How to implement ISO 27001 and ISO 20000 together https://advisera.com/27001academy/blog/2015/03/16/how-to-implement-iso-27001-and-iso-20000-together/
- Incidents in ISO 22301 vs. ISO 27001 vs. ISO 20000 vs. ISO 28003 https://advisera.com/27001academy/blog/2016/09/05/incidents-in-iso22301-vs-iso27001-vs-iso-20000-vs-iso28003/

This material will also help you regarding ISO 27001 and ISO 20000:
- How to integrate ISO 27001 and ISO 20000 [free webinar on demand] https://advisera.com/27001academy/webinar/how-to-integrate-iso-27001-and-iso-20000-free-webinar-on-demand/