The purpose of having a notice period in the employment letter is twofold. First, it is to avoid shocking the employer by resigning overnight without a replacement in place. Second, it is to ensure that the new employee or the person taking charge is suitably trained and made aware of the job's issues and responsibilities. The higher the position you hold, the more responsibilities you have, requiring time for a proper handover, and this is where the notice period comes into play.
Unless specifically mentioned, it is not feasible for any management to allow their employees to use their leaves as a notice period, at least not in full. The employer may request you to personally hand over your duties and ensure there are no outstanding issues for a certain period (about 3-4 weeks). You can negotiate with the employer to adjust part of your remaining leaves as part of the notice period, but it is crucial that both parties are satisfied to avoid any future issues.
Ultimately, the policies of the company dictate how the notice period is managed, and the management may require you to work through your notice period and settle any dues during the Full and Final settlement process.
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