Most of us are familiar with the financial year closing of books and opening of the new financial year.
In a similar manner, most companies follow either calendar year ( Jan - Dec) or financial year (Apr - Mar) for leave accounting.
The unused balance of some leave types (E.g.: Earned Leave) is carried forwarded to the next year or may be encashed or the entire balance is lapsed depending on the leave type.
Also to close the leave year, all pending leave transactions must be cleared/completed.
Once the current leave year is closed, setup holidays for the next year and then ensure leave is granted for the new year.
Leave year ending is critical like financial year accounting as each year, leave accounting must be done.
This may involve indirect financial accounting as leave encashment may be part of the practice.