You just received your property tax bill and are questioning the assessment. It is 10pm at night so you go online and check out Zillow, Trulia or another home valuation site for another opinion. Now you have 3 maybe 4 conflicting prices! Who do you believe? Here is the low down: The town assessment (tax bill assessment) is based on past property sales from over a year ago and is calculated with a state required formula which many times does not reflect your market current value. The online sites use algorithms or their own proprietary formulas, past sales and some local data to calculate your value. What is the best source for your current property value? An experienced real estate agent! An agent is familiar with the current trends, nuances that exist from location to location on the island, and is able to assess your recent upgrades and improvements to the property, unlike the town or a random website. Most agents have been inside many of the homes that your home is being compared to and can give a more realistic market evaluation. Another option would be to have an appraisal done by a certified appraiser. These typically cost $450 to $650 and are usually used for more official documentation such as; financial and estate planning, court or refinancing. Using Zillow or Trulia is a great place to start, but call your trusted agent for an up to date price.