@Rick19744 Thank you very much for your reply. I did not think I should file 12/15/20 either. The reason why I know I am late is because in the initial IRS notice about my company's EIN number (Form SS-4), it says that
"you must file the following form(s) by the date(s) shown"
"Form 1065 12/15/2020".
I am not exactly sure where this date come from.I do not think I filled Section 444. I thought that it may be because that we chose the closing month of the accounting year as "Sept" when we register the company in IL.
