Prince William County officials say they are not trying to foster a community of stool pigeons and tattletales. They just want to make sure fair is fair.

That means targeting personal property tax cheats. County officials are asking residents to let them know about people who live in the county but have their vehicles registered elsewhere, depriving Prince William of tax revenue. A Passat here, an Explorer there, and soon you are talking about real money.

"It's an equity issue," said Steve Ferlotti, count tax administration manager. "They're paying their taxes, and they want others to also pay the same taxes for the same services and same schools."

Acknowledging that some might find it uncomfortable to publicly rat out their neighbors, county government has started a service on the Internet that allows people to point fingers in the privacy of their homes.

Logging on to https://www.pwcgov.org/eservices/taxevader/, residents who suspect a cheater can submit the number of the permanent plate, not a temporary or dealer tag, and the state of registration, and officials with the county Tax Administration Office will start an investigation.

The service even lets people check the status of prior reports. It is all done anonymously. So far there are several dozen open cases that have been reported on the Web site, which went online last month.

Tax administration officials use different databases to get a fix on vehicles and owners. Ferlotti said the office has access to Virginia State Police databases and several private ones.

"Either we go out and try to positively ID the vehicle, or sometimes they own real estate or file taxes here, so we can get a positive match from another source," Ferlotti said. "This is not really to capture people who are delinquent. We know who has been issued a sticker and who hasn't paid. This is more to report people who haven't registered their cars locally."

Board of County Supervisors Chairman Sean T. Connaughton (R), who proposed the system, said he suggested that county tax officials take a look at Fairfax County, which has been successful in catching evaders.

"I get more complaints about this issue than most,'' Connaughton said. "It negatively impacts current property owners because obviously those complying are shouldering the entire tax burden. It also hurts us in getting car-tax reimbursement from the state."

Fairfax County gets 50,000 tips about tax evaders a year, most through its Web site, said Norm Graves, who oversees that county's effort. Graves said Fairfax County already has received 25,000 tips this year.

He said 70 percent to 75 percent of the tips lead to new taxpayers on the county rolls. All told, the effort adds $5 million to $5.5 million in tax revenue to Fairfax, Graves said.

Once an owner is identified as a Fairfax resident, the county sends a polite letter and the effort ratchets up from there. At the extreme end, liens or a "boot" could be placed on the vehicle, Graves said.

Prince William officials said they have no idea how many tax evaders are in the county or how much more taxes might be collected.