NEW YORK — Americans who requested more time to file their 2004 federal income tax returns have a deadline coming up Monday.

That's when tax forms are due for those who filled out IRS Form 4868, the Application for Automatic Extension of Time, to get four additional months to prepare their returns.

The Internal Revenue Service says 9 million taxpayers requested extensions beyond the April 15 deadline this year, or about 7 percent of the expected total of 133 million filers.

Some people have good excuses for being late. There may have been a divorce or a death in the family, making it harder to get all the information needed to file their 1040 income tax returns in April. Or they might not have had the input from business partnerships or trusts to include on their forms.

But in a lot of cases, people request an extension because they're procrastinators, said Mark Luscombe, principal tax analyst at CCH Inc. in Riverwoods, Ill., which provides tax information and services to tax professionals. And they tend to be repeaters, he added.

"Once they file for an extension one year, it sort of becomes a habit," Luscombe said. "I know people who do it regularly who don't have any particular reason they couldn't have had their information together by April 15."

Americans who sought extensions may have gotten more time to file their returns, but they didn't get more time to pay the taxes they owed for 2004.

Included in the application for an extension is the requirement that the taxpayer estimate his or her tax liability for the year and enclose a check for the full amount.

So Americans who didn't file on time because they couldn't pay — or those who filed for an extension and didn't pay enough — now face penalties, Luscombe said.

Under IRS rules, there's a higher penalty for failure to file than for failure to pay.

The penalty for those who don't file is 5 percent per month of the unpaid balance, up to a maximum of 25 percent. The penalty for those who fail to pay is 0.5 percent per month of the balance due, again up to a maximum of 25 percent.

In either case, the IRS charges interest on the unpaid balance, currently at a 6 percent rate.

Margaret Atkins Munro, an enrolled agent who is co-author of "Taxes 2005 for Dummies," said taxpayers sometimes end up requesting extensions because they don't get their material to the tax preparer until April 14. Enrolled agents are licensed by the federal government to prepare tax returns and represent taxpayers before the IRS.

"In those last two weeks before the tax deadline, most preparers are working flat out and can't deal with last-minute filers," Munro said.

"Frankly, most tax preparers are very happy to see you in February and not so happy to see you on April 14."