The Voice of O365 follows the Microsoft Lifecyle Update policy. 

Current version: Skype for Business 2015 Enterprise January 2018 CU8

Latest version: 

Compatability matrix

• Desktop clients: https://technet.microsoft.com/en-us/library/gg412781.aspx
• Mobile clients: https://technet.microsoft.com/en-us/library/dn951412.aspx

Portal updates

• Critical
  Crittical updates to the portal environment (immediate security fixes) will be rolled out immediately to the production environment.
• Non-critical updates
  Non-critical updates, including new features and non-critical bug fixes, are rolled out first to a development environment. This environment is tested with preferred customers before rolling out to public.

Skype for Business updates

• Critical
  Critical updates to the platform will be done in the same evening to ensure the stability of the platform. These critical updates exclude feature updates. Critical fixes include hotfixes supplied by Microsoft.
  
• Non-critical updates
  Non-critical platform updates include feature updates and Skype for Business CU updates will be done in a cycle of release+1 month to ensure platform stability.

Version	Cumulative Update	KB Article
6.0.9319.537	January 2018 (current) / CU8	https://support.microsoft.com/kb/4464355
6.0.9319.534	July/August 2018 / CU7	https://support.microsoft.com/en-gb/help/3061064/updates-for-skype-for-business-server-2015
6.0.9319.516	March 2018 / CU6HF2	https://support.microsoft.com/en-us/help/3061064/updates-for-skype-for-business-server-2015
6.0.9319.510	December 2017 / CU6	http://support.microsoft.com/kb/3061064
6.0.9319.281	May 2017 / CU5	http://support.microsoft.com/kb/4012621
6.0.9319.277	February 2017 / CU4HF1	http://support.microsoft.com/kb/3207506
6.0.9319.272	November 2016 / CU4	http://support.microsoft.com/kb/3199093
6.0.9319.259	June 2016 / CU3	http://support.microsoft.com/kb/3149227
6.0.9319.235	March 2016 / CU2	http://support.microsoft.com/kb/3134260
6.0.9319.102	November 2015 / CU1	http://support.microsoft.com/kb/3097645
6.0.9319.88	September 2015	http://support.microsoft.com/kb/3098601
6.0.9319.55	June 2015	http://support.microsoft.com/kb/3061059
6.0.9319.0	RTM	NA

Security updates

• Critical
  Critical security updates will be peformed based on the severity status. Critical updates will be deployed within the upcoming certificate update window. Within those update windows the servers will be restarted and refreshed with the new updates.
  
• Non-critical updates
  Non-critical security updates will be performed every 2 weeks in the certificate update window. 

Clients

Customers are able to deploy new versions of the skype for business client as they wish. Please ensure that the client complies with the current Skype for Business Enterprise CU.