This month homeowners across the state are getting their property tax bills in the mail. The amount of your tax is based on the assessed valuation of your property.

Most people will pay without even thinking about it, but what if the county assessor was wrong about your property value?

Here's what some say is a best kept secret that could cut your property taxes by hundreds of dollars.

"I appealed my taxes the first year I bought my house in Seattle," said Barbara Alsheikh whose property was over-valued by $28,000.

Fred Wolfstone's property in Clyde Hill was over valued by $70,000. For Loys and Betty Lamb of Richmond Beach, the assessed value was $180,000 too high.

They all got money back by filing an appeal with the county.

"Sometimes the assessor just doesn't get it," said Trudie Walsh, an appeals specialist who represents homeowners who feel their homes are worth less than assessor's valuation.

Despite their best efforts, county assessors make mistakes on the value of thousands of homes across the state every year, but most homeowners never question.

"People just don't know you can appeal." said Walsh. "And that's the sad thing. They just don't know."

But former King County Assessor Harley Hoppe has a more critical explanation.

"It isn't well publicized." Hoppe said.

After years working on the other side of the counter, Hoppe now runs a company on Mercer Island that helps people across the state get valuations reduced when they're too high.

Trudie Walsh, Hoppe's business associate, says any number of factors can make your valuation higher than it should be.

Neighborhoods changing and houses are not selling for as much, increased local street traffic that lowers the desirability, and therefore the market value, a once beautiful view, now lost to trees and buildings.

It could be anything that makes your property worth less than what the assessors use to compare, including cracked foundations and other major repair problems.

"Repair problems are always good arguments," said Walsh. "But you can't go and use repairs year after year. You have to repair your house."

Walsh says many older outdated homes are surrounded with what used to be comparable homes that have been extensively upgraded on the inside. When those upgraded homes are sold, that shoots up the "market value" of the older homes that are still considered to be comparable.

"So many people upgrade their homes but don't get permits." explained Walsh. If assessors are looking at records of comparable homes and see no evidence of building permits, they can't tell the homes have changed.

Contrary to what a lot of people think, the assessors don't physically come to your house every year to look it over.

"No, they don't." said Barbara Alsheikh.

When Alsheikh got her value reduced by $28,000, she had no idea she'd end up working years later as a King County Tax Advisor helping taxpayers understand how assessors came up with those numbers.

"They come out once every six years. The state law allows the assessor to choose a time frame for revalue." Alsheikh explained.

In most counties, assessors only visit your property every four years to seven years. The revalue time frame depends upon the county. Alsheikh says the year your home is physically revalued is the year you're most likely to see a big spike in your valuation.

In the years when the assessors don't physically come to your home, they calculate the value using a complicated combination of condition, maintenance, regression analysis and past sales of comparable homes over the past two to three years.

To their credit, the assessors are often correct, but sometimes those "comps", as they call them, are way off.

Walsh says it's not always to your disadvantage.

"Bigger homes tend to be under-assessed, average homes tend to be assessed correctly, smaller homes tend to be over-assessed." said Walsh.

Hoppe says if you buy a house at below the asking price, you're almost a shoe-in to be over-valued.

"If you just bought a house and you paid $600,000 and it's valued at $700,000, if you don't appeal you'll pay tax on $700,000. If you did appeal, it's almost a synch. If it's a normal market and a fair transaction where you didn't buy it from a relative or something, you'll get $100,000 reduction in value and most of the time you don't have to go to a hearing," Hoppe said.

As soon as you get your next property value notice. go to your county assessor's Web site and verify your property description. We found some county sites to be much more user friendly than others, so look for key words like "property search."

Type in your address or parcel number and double check what the county records say about your property. If that's off, the assessed value could be off too.

Next, find out what other information was used to make your valuation.

If you strongly feel that the information is wrong, file a petition to appeal. You can do it online or at your county board of appeals.

At the informal hearing, you present your case and the assessors representative presents theirs. A decision usually takes at least a couple of weeks.

But make sure you have strong documentation to back up your argument.

"You have to do your research. You're going win it or lose it on the numbers," emphasized Walsh.

You may need pictures, blueprints, statements from real estate agents, the multiple listings and other documentation from experts. It can be time-consuming, which is why taxpayers like the Lambs and the Wolfstone's opt to pay Hoppe's company to do the checking for them.

There are a number of local companies that offer the service and prices vary.

But whether you do it yourself, or hire an expert, it worth the time to at least double check.

Depending on your county's guidelines, you only have 30 to 60 days from the time you get your value notice to petition for an appeal.

King County Board of Appeals Manager David Goff says only about 1 percent of the roughly 500,000 property owners in King County bother to appeal their valuations.

"I think that for the most part, people realize that their assessed values don't exceed the fair market value of property, but when they do, and it does happen, that's why we're here."

As for what percentage of appeals result in lower valuations, Goff says in King County, traditionally more than 50 percent of the people who do appeal get some type of reduction.

If you lose your appeal at the county level, you can file an appeal with the state.

More Information:

Below are links to the Boards of Appeals and Equalization for King, Pierce, Snohomish and Thurston Counties. These websites have answers to frequently asked questions explanations about the appeals process.

King County

Pierce County

Snohomish County

Thurston County

For other counties, simply go to the Web site for the County Assessor, or the County Board of Appeals and Equalization.

State Board of Tax Appeals

www.harleyhoppe.com