To set concurrent leave limits to departments on oneHR, start by clicking Admin in the oneHR main menu. Then click Leave Allowance in the Admin sub-menu.
Here you will see the Concurrent Leave Limits tab on the lower half of the page.
Click Edit to set the limit for each department per day and also per week. Click the Tick to confirm this number. This will prevent too many employees from the same department being on leave on the same day or in the same week.