Shift Incentive Calculation

Hi all
I am working as HR generalist in a leading IT firm and regularly browse through cite HR Mails.
Just have a small query regarding calculation of shift incentive for employees who provide on call support beyond normal working hours.If you have any document regarding the same or guidelines as to how we arrive at the shift incentive amount calculation then that woul be great.
Looking forward to hearing from you
Thanks

there are several instances:
some pay overtime allowance (same caluclations as for workers ie double the normal wages"
A top 5 ITES player pays on incident basis ie a certain sum for email/ chat/ telephonic support... will vary according to complexity of procesess...
add some freebies too like another set of meals etc....
surya

forgot a crucial bit....
brute force ie hiring more manpower or overtime is a major NON COMPLIANCE in COPC/ MBNQA and other business excellence models like six sigma etc....
In one of my prev work roles with a IT giant....
we had tremendous call flow in inbound tech support n worked on several alternatives namely:
a) training a reserve pool of >100 ppl from existing processes to meet the call flow in emergency
b) hiring under graduates to work for a few days in a month @ certain sum....
c) reduced learning curve of tech support people by FAQs database etc
d) lastly we did a Business Process Reengineering, the process now became an outbound tech support
surya