Is raising pigs for your kids' 4-H project a business? How about selling kitchen supplies just so you can buy at wholesale prices? In many cases, the IRS has found activities like these to be hobbies, not businesses. The IRS has issued fact sheet FS-2007-18 to explain the rules for determining if an activity qualifies as a business and what limitations apply if it's a hobby.
Basically, if you don't have a realistic chance of making money, the IRS will want to call your activity a hobby. The big downside of this treatment is that your expenses have to go on your Schedule A, in the section that's reduced by 2% of your gross income from all sources. The expenses also can't be more than the gross income from the activity. Don't worry too much about how to report it; just know that it's a lose-lose situation if your activity is deemed a hobby.
Oh, and even if you don't get any benefit from your deductions because of the rules above, you still get to pay tax on the revenue from the activity. Isn't that generous?
Things you can do to help your activity seem more like a business include having a business plan that realistically shows you could make money on the deal, handling things in a businesslike manner (business cards, advertising, etc.), and, well, making money! If you have a profit three out of five years, the IRS will leave you alone. Of course, you can be in a legitimate business and lose every year; the burden of proof is yours, though.
