Dear Ashok
For Commercial establishments including the company,- provisions of The Karnataka Shops and Commercial Establishments Act 1961 & Rules 1963 are applicable.
As per section 15(1) of said Act, employee is entitled to leave with wages @ one day for every 20 days worked (Which is called as Previlege Leave or Earned Leave or Annual leave).Similarly Section 15(3) stipulates that empoyee is entitled to leave with wages for a period not exceeding 12 days on the ground of sickness(Sick Leave).
There is no provision to carry forward the sick leave. HOwever there is a provision U/S 15(7) to carryforward the Annual Leave not exceeding 30 days. Pleave note that KSCE Act doesn't recognise the casual leave.
The leaves mentioned in KSCE Act are the minimum leaves to be granted. However, an establishment has the liberty to grant more leave over and above stipulated in the KSCE Act. I have observed that, some companies allows casual leave to its employees. If this leave is over and above the 12 sick leaves, there will not be any issues from labour department, otherwise for casual leave also you have to use the nomenclature "Sick Leave"
If yours is a Factory, then Factories Act is applicable which is same as KSCE Act as far as laws regarding leave is concerned
Regards
Ravi P