Monday, September 16 is the final extension due date for almost all 2012 calendar business tax returns (corporations, partnerships and trusts). If you are unable to file your pass-through business return tomorrow on a timely basis, the penalty will usually be $195 per schedule k1 not file per month late.
If you are late with your filing and get a penalty letter from the IRS, do not automatically pay the penalty shown in the letter. If the late filing is for a partnership income tax return and each partner is an individual who files the income or loss timely on their personal return and there are 10 or fewer partners, then you are usually granted an automatic abatement of the penalty, but you will be required to send a letter to the IRS.
This automatic abatement does not apply to an S corporation, however, the IRS offers a first time abatement program that usually gets you out of the penalty, but again, you have to write a letter to the IRS and they do not advertise this option in any prominent area on their web-site.
If you are late with your C corporation and you owe tax, you will face a possible 5% late filing penalty per month late for at least the first five months, therefore, it pays to get this filed timely. If you do not owe tax, there is usually not a penalty, but you will get a letter from the IRS at some point.