Hi
First of all you have to inform the policy of your company on leaves. In general let me explain, the year is taken as calendar year[Jan to Dec] and Casual leaves are 6 and so are Sick leaves in a year with earned/privileged leaves being 15 days or 1 per every 20 working days depending on the policies of the company. Supposing your company has the policy of 6 days of CL and SL with EL being 15 [to be credited after completion of the year unless the employee exits]. Roughly the CL and SL will be 1/2 day per month [each] and in the above instance, you may say that pro rata the employee will be getting 5.5 days of CL and 5.5 days of SL if he happens to stay till Dec 31st of the year. He should be in loss of pay going by his record of leaves taken thus far. If it is a case of full and final settlement it is a different issue, else he ought to have his salary deducted by now. Talk to the management before you issue any letter to the employee.
Thanks and Regards