Because home values have fallen, you might have been told that you can save a bundle on your property taxes.

And maybe you can, the legitimate way—by asking your county assessor’s office to review your property’s valuation.

Just don’t expect to lower your tax bill by dealing with “property tax reassessment services” or “tax assessors” who go door to door. There’s an upswing in efforts to trick homeowners into paying for such services that can be done at no charge, courtesy of your tax dollars.

Official-looking letters

In the most popular ruse, an official-looking letter promises to cut thousands off your current property taxes by having the sender file a property reassessment or “decline in value” request on the homeowner’s behalf. The fee is usually about $150 or more.

These letters, already received by tens of thousands of property owners in western states, usually list the homeowner’s name and address and a specific amount of expected savings.

All that’s required, the letters claim, is to complete an authentic-appearing form and return it with payment. Then, the claim goes, the sender will file the paperwork on your behalf. Some letters warn that homeowners who fail to respond could face additional fees or become “ineligible for future tax reassessments.”

Not true, say officials.

“These scam artists ripped off thousands of homeowners throughout California for property reassessment services readily available free of charge,” charges Attorney General Edmund G. Brown Jr., who sued brothers Sean and Michael McConville and their companies, Property Tax Review Board and Property Tax Adjustment Services.

Scams are moving east

Another Property Tax Review Board owned by Michael McConville sent letters to property owners in Arizona and Nevada. Arizona Attorney General Terry Goddard recently sued McConville—along with Carmen Mercer, a leader of the Minuteman Civil Defense Corps whose volunteer members patrol U.S. borders to prevent anyone from entering the country illegally—for owning the post office box cited in those mailings.

Nevada officials, meanwhile, issued a fraud warning about the board’s solicitations. Neither McConville brother nor Mercer could be reached for comment.

Although the company names may change, expect this type of rip-off to move east.

Already, West Virginia police report that scam artists are posing as employees of a county tax assessor’s office. They visit homes allegedly to take measurements for an reassessment, then try to charge residents for the unsolicited service.

The bottom line: Ignore any letter that promises a property reassessment or other tax-lowering service for a fee. Instead, ask your assessor’s office whether you are entitled to pay less in property taxes because of a lower home value. But be aware that depending on where you live, property taxes may be based on a home’s replacement cost or other criteria, not its market value.

Sid Kirchheimer is the author of Scam-Proof Your Life.