If you have days within your company with everyone must take such as public holidays or forced shutdown periods then you should look at Mandatory Company Holidays.
By using Mandatory Company Holidays you get two benefits:
1) Employees will have these days automatically removed from their allowance
2) Any timeoff booked which includes a Mandatory Holiday will not have that day double counted.
To setup Mandatory Company Holidays you need to do three things:
1) Enable "COMPANY HOLIDAYS MANDATORY" By going to: Administration > Company >Settings > Timeoff settings (global) Once in the time off settings screen, if you scroll down to the section entitled 'Company Holidays' You will need to set the 'Company Holidays Mandatory' field to 'Yes' (also you can set this in Site options under HR/Sites for individual sites should this only apply to certain employees/locations/companies etc)
2) Choose from which timeoff type you wish these mandatory holidays to be removed by setting "Default deducting type" - You can do this by going to Administration > HR > Time off management > Time off Types, editing the type which you wish to deduct the mandatory days from and setting the 'Default Deducting Type' field to 'Yes'.
3) Add the actual holidays themselves under Time & Attendance> Holidays
Once you have this enabled, employees will automatically have the Holidays removed from their allowance.
Your company has enabled Company Holidays Mandatory, assigned these days against Holiday and added the days. For simplicity sake, these days map the UK public holidays giving 8 days in total.
Fred works 5 days per week and is entitled to a total of 28 days Holiday per year - from the beginning of the year his allowance will show as:
In this instance, Fred has 6 days which have been already taken and 8 mandatory days automatically deducted from his allowance giving him a total of 14 days remaining. By adding all of these values together, we can see that Fred's full annual allowance is 28 days.
Fred then requests timeoff from 22nd December to 26 December inclusive - the system looks initially at whether each of the days are working days for Fred (which they are) and then checks for Company Holidays and in this case finds 25th December and 26th December hence it only deducts three days from his allowance as the 2 mandatory days are already deducted.