Dread on Arrival

Assessors also canvass neighborhoods on occasion and keep a watchful eye on building permits to track renovations that might alter a home's value.

"People think that because homes are assessed at the full market value that we should be on top of every single sales price, and that's really not how it works," said Janet Coldsmith, director of Fairfax County's Real Estate Division. "We're looking at a group of sales in a neighborhood and trying to come up with the most likely value."

The goal is to assign reasonable values to properties so that homeowners carry their fair share of the tax burden, said John McIlwain, a senior fellow at the Urban Land Institute. "Valuations are always a best guesstimate," he said.

These valuations are listed on tax rolls that legislators use to figure out the taxable property base in their districts. They then set rates for those properties at the levels needed to fund the jurisdiction's many needs: schools, roads, firetrucks, etc.

The assessment multiplied by the tax rate (usually expressed in so many dollars per $100 or $1,000) equals the tax bill -- or the out-of-pocket cost for a homeowner.

"People constantly want to appeal based on what they think their tax bill will be," said Todd Kaufman, the Loudoun County assessor. "But that is not a bona fide reason to appeal because that's an issue very separate from the assessment or the value of the home."

Just because the assessment is up does not mean the tax bill is up proportionally, if it's up at all. The determining factor is the tax rate. And that isn't all Both the District and Maryland have laws designed to cap increases when prices jump. Virginia doesn't.

The subjective nature of some of these elements is what can make property taxes rankle, said Stanley J. Fineman, president of Wilkes Artis, a D.C.-based real estate law firm.

"With the income tax, for instance, the government says: 'Here is what you earned, send me half of it,' " Fineman said. "The real estate tax is very unusual in that it's subjectively based. It's a rate set by legislators that is applied to a number that somebody determines to be the value of your property."

That's why there's an appeals process. Some areas offer online applications or hearings by phone.

The rules and laws that affect appeals vary by jurisdiction. The assessment notice itself includes some of the steps needed to appeal. All local jurisdictions also maintain Web sites that offer more information and, in some cases, allow appeals online. (See charts.) But most assessment offices agree that before filing, homeowners should first call their assessment offices to discuss their concerns.

"If your questions are answered, there's no sense in filing paper," said Rice of Arlington County. "If they're not answered, you might be better positioned to appeal if you understand how your house was assessed."