Add Prefix To ID

Create a year Table with incremental ID's
Create a Expression to create the custom Prefix
MyPrefix= concatenate("CRE",YYYY,ID)
NOTE instead of 2016 I would extract the Current Year

Perhaps update the Year table with the reference if needed for reporting
Use the latest value from a view list, page 1 at the time sort ID Desc. this way you always get the lastest PREFIX.

Take a look to the following post for more details
http://community.k2.com/t5/K2-blackpearl/Add-Prefix-To-ID/m-p/87922#M27350