Answer
Unused Annual Holidays remain available until they are taken, cashed up where allowed, or paid out in a final pay. They do not reset to zero each year.
Lightning Payroll keeps Annual Holidays in weeks. Each anniversary grants entitled weeks, leave taken deducts weeks, and a cash-up deducts the weeks paid instead of taken.
To review the balance and how it was built up, open the employee under Employees >> Leave >> Leave Entitlement/Adjustments and click How is this balance calculated?. Do not cash up more than the allowed amount for the current entitlement year.