I have a client (partnership/LLC) that filed a 1065 last year and I forgot that they went down to one member last year so I extended the 1065 before they got me their stuff.  Can I file an 1120S this year for them - as they'd rather be treated this way than report on Schedule C?  Will they get a late penalty?  If I explain on the 2553 that the extension was filed for the 1065 properly, will I have to protest a fine?