"People tend to lose their receipts. They need to keep all their receipts and invoices, throw them into a file," says Jeffrey J. Spengler, a principal at the CPA firm of McCrory & McDowell LLC, in Pittsburgh.

But don't go overboard. Homeowners often erroneously include home improvements for which they were reimbursed.

"We had a pretty wicked ice storm here a few years ago, and it seemed like everyone in my neighborhood had their roof replaced," Spengler says. "Since it was storm-related and paid for by insurance, this doesn't add to the value of your home."

And don't discount something just because it doesn't fall neatly into the home-improvement category. It still might be useful in offsetting possible capital gains. If you spruce up your house with a new paint job to make it more attractive to buyers, that counts as a selling expense, Spengler says. Selling expenses lower the amount you realize on the sale of the home, which in turn lowers the profit you make.

Home basis in black, white and gray
Remember, too, that home improvement versus repair is a gray, rather than black-and-white, tax issue. It makes good sense to run any construction projects by your tax adviser, accountant or real estate agent for guidance on whether the project will pass the IRS test for increasing home value.

And if the project doesn't pass?

"When an audit question comes up with the IRS about a home improvement, I'll have the auditor contact the president of the local board of Realtors here," says J. Michael Roberts, owner of Creative Tax Solutions, an accounting firm in Laguna Hills, Calif., and chairman of the California Association of Realtors' Real Estate Finance Committee.

Local real estate agents can advise the IRS on what they believe are legitimate home improvements that add value. Indeed, Roberts points out that such definitions can vary by region and neighborhood. For example, in most cases, a stove replacement might be considered simple maintenance. But if you live in a posh neighborhood and you replace a four-burner no-name electric stove with a six-burner upscale Viking, along with adding other pricey built-in appliances, then you've transformed your kitchen into a gourmet eatery worthy of Emeril and, thus, boosted the basis of your home.

"It's really funny how in one area something that might be considered an enhancement might be standard in a different area," Roberts says.

Figuring your home-sale gain or loss
To determine whether you made a profit and might owe taxes on your home's sale, start with the selling price. This is the total amount received for your home, including money, all notes, mortgages or other debts assumed by the buyer as part of the sale.

Next, subtract any selling expenses, including advertising, painting or other upkeep performed to improve the appearance and marketability of the property. This will give you the amount realized.

Now subtract your adjusted basis from the amount realized. The result is your gain or loss.

You'll come out tax-free if your gain is $250,000 or less and you're a single seller; twice that amount if you and your spouse sell the house. You also must have lived in the home for two of the last five years that you owned it.

There is an exception for military personnel to the time-of-residence requirement. Members of the armed forces can suspend the five-year ownership-and-use test period for the time during which the member, or his or her spouse, served qualified official extended duty.

If your gain is more than the limit, it could be time to start digging through your records to find documentation that could help you increase your adjusted basis.

And if you sold at a loss, sorry. There is no tax break for these unlucky sellers.

Jenny C. McCune is a contributing editor based in Montana.

Bankrate editorial assistant Leslie Hunt contributed to this story.