Tax deadline: Why you get until April 17 this year to file your return

The tax deadline for filing 2011 federal income tax returns comes two days later than usual. For this, last-minute filers have President Lincoln to thank. 

Happy Emancipation Day, everybody.

Thanks to an unusual holiday in the nation's capital city, celebrating the end of slavery there in 1862, taxpayers across America have been liberated from the tax man for an extra day.

You have until April 17 to file your federal tax returns, or to apply for an extension. Typically the deadline each year is April 15.

Here's why things are different this year: April 15 came on a Sunday, with no mail pickup by the US Postal Service. Then comes April 16, which is Emancipation Day in the District of Columbia. The district's celebration doesn't make it a federal holiday, but the Internal Revenue Service says that "according to federal law, District of Columbia holidays impact tax deadlines in the same way that federal holidays do."

The result: taxpayers have two extra days. But if you're requesting an extension, the IRS says you'll have to file your return by Oct. 15 (not until Oct. 17).

Of course, millions of Americans have already filed their taxes, to get refunds as quickly as possible – or just because they don't like to wait until the last possible moment. In all, the IRS expects to receive some 144 million tax returns this year.

Remember that, even if you file for an extension, the IRS still expects you to pay any money you owe by the April 17 deadline. You can file electronically, via the IRS "Free File" system or through downloaded tax software. If you can't pay the full bill on time, some alternative steps are listed in a separate story on last-minute filing tips.

Most states follow the pattern of the federal deadline. According to CrossLink, a software provider for tax professionals, Tennessee residents must file by April 16, and five states have tax deadlines that fall on later dates, ranging from April 20 through May 15. Those states are Hawaii, Iowa, Delaware, Virginia, and Louisiana.

The District of Columbia began official Emancipation Day celebrations in 2005, so the holiday's impact on the tax calendar is relatively new. In 2011, Emancipation Day helped push the tax deadline to April 18. 

The holiday harks back to April 16, 1862, when Abraham Lincoln signed a law to free some 3,100 slaves in the District of Columbia, eight months before the Emancipation Proclamation liberated slaves in the South. The District was the only part of the US that compensated slave owners for freeing enslaved persons they held, the district's website says.

Among the other noteworthy details, mentioned on the district's Emancipation Day web pages: During the Civil War, Sen. Charles Sumner of Massachusetts confronted President Lincoln by saying, “Do you know who is at this moment the largest slaveholder in the United States?” The senator said Lincoln was, because the president “holds all the slaves of the District of Columbia.” 

According to the website, Sumner's legal reasoning was controversial (he was referring to federal power to “exercise exclusive legislation” in the district). But he used this argument to press for abolition in the national capital.

Of some 209,000 black men who served as Civil War soldiers, 3,265 were from Washington, D.C., the website says.