If you work overtime after hours on your scheduled tour of duty, and you were not informed of the overtime prior to the commencement of this tour of duty, it is classed as unplanned overtime and you cannot claim overtime for the first 30 minutes worked.
For example, if your tour of duty is 14:30 x 22:30, you cannot claim overtime until 23:00.
Any overtime you claim after that is at time and a third, for payment, or if you wish to claim time off, for the overtime, then for every completed 15 minutes, you are entitled to claim 1 unit and for every 3 units you work, you are given 1 bonus unit.
If you work unplanned overtime on 4 occasions during the same week then on the 5th and any other occasion in which you may have to work overtime you no longer lose the first half hour for the rest of that week.
If you were asked to work overtime prior to the commencement of your tour of duty this is planned overtime and you do not lose the first half an hour when calculating how much time you have worked over.