If you file your return on or before March 1, 2013, you must also payyour tax on or before March 1. If you file on March 1 and then pay your tax on April 15, you most likely will be subject to the penalty.
Therefore, to file and pay your tax without the penalty, make sure to file between March 2 and April 15, 2013. Otherwise, you may owe a penalty you were not counting on.
Paul Neiffer CPA