If you do not file the necessary form to extend your personal return and end up owing taxes, failure to properly extend the form will result in the large penalty of 5% per month of the tax due up to a maximum penalty of 25% of the tax due plus interest. Best to not miss filing that extension due to this high penalty.
Your TDF 90 -22.1 Form reporting foreign financial, bank accounts, etc., must be received by 6/30/11 at the Detroit address on that form. No extensions can be obtain. Late filing can result in penalties of $10,000 or more.
Your Form 5471 for Foreign Corporations, 8865 for foreign partnerships and LLCs, 3520 for foreign trusts and Mexican Fideicomisos, and Form 8858 for disregarded entities are all on the due dae of your personal return or its extended due date if that is later and you have filed an extension.