Yes, you can claim the exemption of leave encashment while filing your IT Return. The deduction will be allowed even if the employer has not provided in Form 16.
Leave encashment received by Central or State Government employees at the time of retirement or resignation is fully exempt.
From my understanding, you are referring to a non-government company. In this case, leave encashment will be exempt u/s 10(10AA)(ii) up to the least of the following:
1. Actual leave encashment amount
2. Average salary* for last 10 months
3. Salary per day * unutilised leave (considering maximum 30 days leave per year) for every year of completed service (F)
4. Maximum allowed as deduction 3,00,000
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