assuming there is no disaster declaration in effect for your state, your choice. if nothing is on line 21. either file now but you may have to amend or file an extension to avoid the need to amend.  I would choose the later. if there's an amount on line 21 you need the k-3 so file an extension. if you have a state return some states require a separate extension others grant an extension if a federal extension is filed.  any taxes owed would be due Tuesday (unless a disaster declaration grants more time)