The more important point is that the ledger is incorrect at the end of every month, because it does not reflect the adjustment for Employment Allowance for that...
If you set the active tax year to 2025/26, the 2024/25 P60s should appear in the Documents tab for each employee.i.e. Payroll > Employees > [employee name] > Do...
If you mean the notification to tell HMRC that you have run the final payroll and the year has been closed, the flag should be included in the final (month 12) ...