ESS changes for W-4

[Rick Sample]

I have a request to create a WF for changes to user's W-4 data via ESS. 
I am doing some preliminary research to give some development estimates.  
 
I know we have Address Change, Time Approval, and Leave requests. 
I understand the lock, unlock, and check for locks, etc. 
 
What I don't know is the business object and event I would use for W-4 Tax changes? 
They want a WF to "Lock" the object and route to our HR Service Center 
to verify / update and release locks. 
I see EMPLOYEET object but not sure if this is the one I want.
 
We are on 4.6c