As you may or may not know, the deadline this year for filing your federal (2010) income tax return has been extended to April 18th, 2011 (instead of the typical 15th). This is due to the IRS observing the Emancipation Day in the District of Columbia.
However, not all states are following the IRS’s lead, so some state tax returns will still be due on April 15th. You should double-check your state to determine this years deadline.
Here in California, the 15th is still listed as the official deadline, but they go on to say, “Due to the federal Emancipation Day holiday on April 15, 2011, tax returns filed and payments received on April 18, 2011, will be considered timely.”