even if you couldn't pay you should have filed an extension. the failure to pay penalty is only 1/2% a month but the late file (filing after due date without a valid extension) is 4.5% per month for up to 5 months plus the late pay penalty. then only the failure to pay penalty applies. your 2 months late (fraction of a month is a whole month) so the penalty should be 10% + interest.
