Hi,
In our company, we have a practice of consolidating organization-wide headcount on a monthly basis so that the HR department and all other departments are on the same page regarding each department's current manpower. We also maintain all the necessary details of all the employees so that every piece of information is available to us in one file. We maintain a separate Management Information System (MIS) for attrition calculation and attrition MIS. I am attaching a sample format of our monthly/master MIS. Hope this is of some use to you.
Regards,
Deepak