Dear Subhabrata,
Leave encashment and notice period are both similar for the organization. Hence, the basis for both remains the same. If an organization deducts notice period shortage from basic salary, the leave encashment is also done on basic salary but only in F&F.
Some organizations also apply this formula for any leave encashment allowed over and above a permissible limit to keep numbers.
Everything will depend on the organizational environment. If it has sufficient leaves provided and has no restrictions on leave approvals (business does not deny leave to employees), then it can fix restrictions to avoid misuse and unnecessary cash outflow.
For example, if the work pressure is not much and employees can take leave as and when wanted, the organization can fix limits on leave carry forwarded, and the encashment can happen only after a certain number of leaves accumulate or during the employee's exit.
It's the organizational need that dictates how it wants this cost to feature as empowering/restricting/controlling.
Regards,
Shridhar Bhagwat