Filing one's taxes ranks close to battling food poisoning on the master list of life's little unpleasantries. Granted, most folks do ultimately get refunds -– an estimated 78 percent of filers got refunds in 2003, according to the most recent figures provided by the IRS. But that doesn't make the process any less confusing and frustrating.

Fact is, mistakes abound when it comes to filing taxes. The IRS estimates that 12 percent of paper returns will have some kind of error. Happily, the silliest mistakes -– not signing your forms, making mathematical errors and writing illegibly -– are also the easiest to fix. Just use tax-preparation software and file your return online, advises Anthony Burke, an IRS spokesman. “It’s faster and inherently more accurate,” he says.

But not all of the biggest tax blunders are easily found -– or corrected. We’ve collected five of the worst, along with recommendations on how to avoid making them in the first place.