Here is a word from the Goodfellas at the IRS:
IRS Tax Tip 2013-58
April 15 is the annual deadline for most people to file their federal income tax return and pay any taxes they owe. By law, the IRS may assess penalties to taxpayers for both failing to file a tax return and for failing to pay taxes they owe by the deadline.
Here are eight important points about penalties for filing or paying late.