WASHINGTON — As year end approaches, the Internal Revenue Service today strongly encouraged paid tax return preparers to register now for their new or renewed Preparer Tax Identification Numbers (PTINs) to avoid any last-minute rush.

Starting Jan. 1, 2011, use of the PTIN will be mandatory on all federal tax returns and claims for refund prepared by a paid tax preparer. Individuals who, for compensation, prepare all or substantially all of any federal tax return or claim for refund must use PTINs. Paid preparers must apply for a new or renewed PTIN through the new sign-up system at www.irs.gov/taxpros.

“We urge you to register now if you plan on preparing tax returns in 2011. The holidays are approaching and it may be tempting to let this slip,” said David R. Williams, leader of the new Return Preparer Office. “Our advice is to register now. It takes 15 minutes, and you’re done. Over 380,000 preparers have registered so far.”

Any preparer who obtained a PTIN prior to the new sign-up system launch on Sept. 28, 2010, must apply again. Generally, preparers with existing PTINs will be permitted to retain their existing numbers if the information they provide during the sign-up process matches what the IRS currently has on file.

The PTIN is a nine-digit number that preparers must use when they prepare and sign a tax return or claim for refund. Previously, PTIN use was optional in place of the preparer’s social security number. Mandatory use of the PTIN is part of a broader effort by the IRS to regulate the tax return preparation industry and improve services for taxpayers.