What's the best tax break available to Jane and John Q. Public? If they're homeowners, it's selling their house.

Homeowners already know the many tax breaks that Uncle Sam offers, most notably mortgage interest and property tax deductions. Well, he also has good tax news for home sellers: Most of them won't owe the Internal Revenue Service a single dime.

When you sell your primary residence, you can make up to $250,000 in profit if you're a single owner, twice that if you're married, and not owe any capital gains taxes.

"Most people are not going to have a tax obligation unless their gain is huge," says Bob Trinz, a senior tax analyst at RIA, which provides tax information and software to tax professionals.

Some sellers are surprised by this break, especially if they've been in their homes for a while. That's because before May 7, 1997, the only way you could avoid paying taxes on your home-sale profit was to use the money to buy another, more-expensive house within two years. Sellers age 55 or older had one other option. They could take a once-in-a-lifetime tax exemption of up to $125,000 in profits. And in all instances, there was tax paperwork (Form 2119) to fill out to show that you followed the rules.

But when the Taxpayer Relief Act of 1997 became law, the home-sale tax burden eased for millions of residential taxpayers. The rollover or once-in-a-lifetime options were replaced with the current per-sale exclusion amounts.

"There is some logic to this law change because most people under the prior rules didn't recognize a taxable gain because they rolled it over into another residence," says Trinz. "The change essentially makes it easier to dispose of your residence."

Still some requirements to meet
If you used pre-1997 rules for residential sales, don't worry. That doesn't disqualify you from claiming the exclusion on any residential sales now. The law change applies to all sales since it took effect.

Another bonus of the new rules: You don't have to buy another home with your sale proceeds. You can use the money to travel to Europe in style, buy an RV and drive across the country or get all those designer shoes you never could afford before.

Even better, there's no limit on the number of times you can use the home-sale exemption. In most cases, you can make tax-free profits of $250,000 (or $500,000 depending on your filing status) every time you sell a home.

Ah, but we are talking taxes here. You did notice that phrase "in most cases," didn't you? Before you put a "For Sale" sign in the yard, you need to make sure your house-sale situation is one of those "most cases."

First, the property you're selling must be your principal residence. That means you live in it. This tax break doesn't apply to a house or other property that you have solely for investment purposes. In those cases, the usual capital gains rules apply.

You can, however, turn a rental house into your primary residence, making the sale of it eligible for the exclusion. This is accomplished when you meet the IRS use and ownership tests: You own and live in the home for two out of the five years before the sale.