No matter how long an employee has been working, he or she has the right to be paid for leave accrued during that time. When your workers leave - even if you have dismissed them - they must receive pay for any statutory leave they are entitled to in the current leave year but have not taken.
When you offboard employees, Air shows you how much time off that employee has remaining. You can use this number to calculate the pay they are entitled to.
Read more at NI Business Info (Formula for calculating pay due)
Read more at ACAS (Help & advice for employers and employees)