... don't turn up for an overtime shift, If you are off sick or for any other reason during your 9 -5 normal Mon - Fri shifts you are absent and will be recorded as being absent from work... BUT as overtime is optional can they legally mark you as absent, (Three absences in 3 Month = a warning) Understandable as you are contracted to work a set amount of hours BUT overtime is optional, So is it legal to mark someone as absent which could in fact result in an official warning