The leave requests which are already submitted and not started the Rejoin task (Not submitted the ‘Employee Rejoin Confirmation – Requestor’ task) can be cancelled thru the  'Leave Cancellation' page under Leave Management  module.

Leave Management -> Leave Cancellation

Once the rejoin process started then it can not be cancelled. The cancelled leave’s eligibility can be reused.

Click below link to view create Leave Cancellation Video: