We study multitasking scheduling and due-window assignment problems in a single machine, which can be found in various application domains.In this paper, we study two problems, the rst objective is minimise the earliness, tardiness, due-window starting time, and due-window size costs, the second objective is minmax common due-date with completion time penalty, then we provide polynomial time solutions. Finally, the experimental results show that the proposed methods are e ective.