This is easily achieved in the Absence tab of the Employee Form. You simply decide on the amount of unused balance that can be carried forward and let Focus do the rest. This works for all employees, whether they have days or hours balances.
An employee has a Personal holiday allowance of 25 days. You want to allow them to be able to carry up to 3 unused holiday days from the end of the current holiday year into the new holiday year.
Even though the current holiday year might not be over, any days brought forward will already show in the next holiday year and be included in its Total Allowance.
In the example above, the employee has a current End Balance of 3 days. This means that all 3 of those days can be carried forward if no more holiday is booked before the end of the holiday year.
* This also works for the Public and Lieu leave channels, if the employee has these enabled.