Can i cancel COE and reapply later?

Hi,

I have received my COE for study in school of japanese language but I recognized that I need time to finish all the things at my homecountry before I can go to Japan. So I'd like to cancel COE and after 6 months or more reapply for student visa and COE.
What should I do to cancel COE certificate? Will I be banned from Immigration if I cancel it now in order to reapply later? Should I explain the situation to someone and to whom then?

Does anyone knows is it possible to cancel it due to your own circumstances and get the same type of COE later in the year or it can be rejected because I didn't use this one?
I don't want to be banned but I really would prefer to finish my work before I can go.

Thanks in advance.