Earned Leave encashment

Hello.

Is there any specific rule under INCOME TAX RULES for allowances from salary?

There is Rule 3 for Valuation of Perquisites. Is this rule applicable to allowances as well like 'Earned Leave Encashment' received by government employees upon retirement?

Actually our client is a company in which 56% of the shares are held by central Govt.

When we did valuation of perquisites like 'Rent Free Accomodation' for its employees, Rule 3 became applicable on them and they were considered non-govt. employees.(as those were the employees on deemed deputation basis)
 

Now, we have to do valuation of 'Leave Encashment'. What should we consider them? Govt. employees or Non-govt. emp[oyees??

Please suggest. Its urgent