Answer
The sick leave carry-over cap limits how much unused Sick Leave can be carried forward. The standard cap is 20 days unless a more generous agreement applies.
To review it, open the employee under Employees >> Leave >> Leave Entitlement/Adjustments and click How is this balance calculated?. The Sick Leave section lists each yearly entitlement, any Carry-over limit applied line, and the current balance.
If the employer provides more generous sick leave, update the NZ sick leave carryover cap (days) field under Leave Settings. Do not use manual adjustments to bypass the cap unless you are recording a deliberate employer-provided additional entitlement.