Read your contract. It may wwell have a clause requiring you to give reasons for absence.ostensibly this is to assist them to help you back to work. Generally for absences of less than seven days a sick note is not required, self certification being the tem used, but you often have to give more detail than "I was Sick". If you really dont want to tell them, then you should look to why you dont. Were you ill? Couldnt you tell them what you had. beleive me, when you start describing food poisoning sympt9ms to them they often dont go any furhter.