The Internal Revenue Service on Tuesday opened the 2011 tax filing season by announcing that, because of a Washington, D.C. holiday, taxpayers have until April 18 to file their tax returns.

The IRS reminded taxpayers impacted by recent tax law changes that using e-file is the best way to ensure accurate tax returns and get faster refunds.

Taxpayers will have until Monday, April 18 to file their 2010 tax returns and pay any tax due because Emancipation Day, a holiday observed in the District of Columbia, falls this year on Friday, April 15.

By law, District of Columbia holidays impact tax deadlines in the same way that federal holidays do; therefore, all taxpayers will have three extra days to file this year. Taxpayers requesting an extension will have until Oct. 17 to file their 2010 tax returns.

The IRS expects to receive more than 140 million individual tax returns this year, with most of those being filed by the April 18 deadline.

The IRS also cautioned taxpayers with foreign accounts to properly report income from these accounts and file the appropriate forms on time to avoid stiff penalties.

“The IRS has made important strides at stopping tax avoidance using offshore accounts,” said IRS Commissioner Doug Shulman. “We continue to focus on offshore tax compliance and people with offshore accounts need to pay taxes on income from those accounts.”

The IRS also reminded tax professionals preparing returns for a fee that this is the first year that they must have a Preparer Tax Identification Number (PTIN). Tax return preparers should register immediately using the new PTIN sign-up system available through www.IRS.gov/taxpros.

For most taxpayers, the 2011 tax filing season starts on schedule. However, tax law changes enacted by Congress and signed by President Obama in December mean some people need to wait until mid- to late February to file their tax returns in order to give the IRS time to reprogram its processing systems.

Some taxpayers - including those who itemize deductions on Form 1040 Schedule A - will need to wait to file.

This includes taxpayers impacted by any of three tax provisions that expired at the end of 2009 and were renewed by the Tax Relief, Unemployment Insurance Reauthorization, and Job Creation Act Of 2010 enacted Dec. 17. Those who need to wait to file include:

Taxpayers Claiming Itemized Deductions on Schedule A. Itemized deductions include mortgage interest, charitable deductions, medical and dental expenses as well as state and local taxes.

In addition, itemized deductions include the state and local general sales tax deduction that was also extended and which primarily benefits people living in areas without state and local income taxes.

Because of late Congressional action to enact tax law changes, anyone who itemizes and files a Schedule A will need to wait to file until mid- to late February.