This site http://www.ctpersonalpropertytax.com offers a totally anonymous means of reporting people who you think may be cheating on their car or personal property taxes. I know that many people call the Assessor's Office but it cannot take an anonymous report. This is a quote from the site:
"Did you ever sit in line at your local bank drive-up and wonder why the driver of the Florida registered Hummer in front of you would want to have an account there? That 4-wheel drive must really come in handy during those Florida winters! Did you ever wonder why you see those same people in the Vermont registered Mercedes 500SL every weekend at your local pizza parlor?
Many Connecticut residents register their vehicles in other states to avoid paying sales taxes and local property taxes. These vehicles are easy to spot because they’re parked in your neighbor’s driveway displaying the state marker plates of their vacation home! If you ask them, they’ll provide answers more entertaining than those of ENRON ex-officials testifying before Congress. There is ONE place where you will NEVER see them. You’ll never see them waiting in line for a Connecticut emissions test!
An even bigger problem…..many more Connecticut residents register their vehicles in Connecticut but use an address/tax town other than their residence where the vehicle is located. These are what we refer to as “stealth” cheats because they are not readily visible. This is most prevalent in the Cities where mil rates are high and where insurance premiums are double that of the suburbs."