On the pain scale, preparing income taxes falls somewhere between a visit to the doctor and a visit to the dentist. All are necessary in the long run, but oh so easy to put off until tomorrow, or the next day, or the day after that.

But why do we procrastinate, foot-drag, dither and delay filing our income tax, even when we owe nothing or can claim a refund? After all, as Ben Franklin observed, taxes rank right up there with death in life's short list of inevitabilities.

Yes, you can delay the paperwork by filing an extension, IRS Form 4868, but you cannot delay the paying. What's more, failure to do either can seriously restructure your financial picture for the worse.

Kathleen Vohs, assistant professor of marketing at the University of Minnesota's Carlson School of Management, offers a clinical explanation for procrastination in general.

"People first choose to regulate their emotions, meaning that they would rather focus on feeling good for longer than deal with this unpleasant task," she says. "When we are faced with an averse task, people who would rather manage their emotions first will give priority to feeling good for longer, and consequently put off that unpleasant task until the very last minute."

Money coach and author Ruth Hayden knows what drives her foot-dragging clients:

"Usually, any form of procrastination is either fear or rebellion. How much am I going to owe? Are 'they' going to take it away from me? What if I can't do this? So they just avoid it," she says.

Steve Fishman, attorney and author of "Working for Yourself", says there may be more nefarious reasons why some taxpayers delay or skip filing altogether.

"Maybe they are doing other kinds of cheating and are afraid that if they file, the IRS will discover some of those bad things," he says. "There are many, many people who don't file and they get away with it for years and years. But you never know when you'll get caught, and you'll face really big penalties when you do."

Then there are the protesters who claim that income taxes are inherently illegal. You can read more about them in a special section of the IRS site devoted to frivolous tax arguments.

"These are the fringe groups that claim it's unconstitutional. These people have meetings and Web sites and stuff, but it's all ridiculous," says Fishman. "The latest one who got caught was Wesley Snipes. He listened to some of these people and claimed it was not constitutional. That's not going to work."

Slacker statistics
The IRS estimates that 10.3 million individuals will apply for a six-month extension this year out of almost 140 million individual Form 1040 filers. That's slightly more than asked for extra time last year, even though this filing season taxpayers have added incentive to complete their returns; filing is the only way to receive an economic stimulus rebate check later this year.