The penalty for late filing of a Sub S return (this includes not filing a timely extension) for 2011 is $195 per month x number of shareholders (up to 12 months).
When the penalty is accessed, you should call the 800 number on the notice. Tell the agent, if this is true (they will check), this is the first and last time a late filing will happen. Please abate the penalty.
Thus far this has been 100% successful.