A contract for a salaried position may say something like “you will work 40 hours a week but you maybe have to work some moderate overtime to complete tasks at certain times throughout the year.” (Probably better worded than that) but that means they can expect you to work overtime every now and then if there is a deadline or a project that requires it. But if its every week or an unreasonable amount of overtime per week then you should be compensated with time in lieu or extra money. It all depends on your contract.