In Timesheets, you can change your entry type (this is what type of entry is on the timesheets):
When selecting in the drop down, you can change the entry type from work to leave and from this select from the list of leave types that are setup in your Guardhouse account.
This is useful for shifts that are last minute blow outs or sickness as it enables you to change the shift from work, to a leave or absence type. Once you alter this entry from work to leave, it will no longer flow through to be invoiced, and instead only flow through Paysheets once approved and will display at the rate that you have setup for this leave type.