On January 4, 2016 the Nassau County Assessor published the new real estate tax assessments for all residential and commercial taxpayers. The filing period of the Assessment Review Commission (ARC) to protest, grieve and make complaints of the assessments is open until March 1, 2016. Since the assessments are not made at full market value the ratio of assessment to market value changes every year. The market values on the Nassau County website are artificially much lower than the actual values that you are being assessed at because the Assessor does not use the current ratio. The estimated market value assigned by the Assessor is probably higher this year than last year. This is because the County does not want to show you how high they are actually assessing your property - in essence, they are misleading website visitors.
Everyone should have their assessment professionally checked every year; if no timely protest is made you are stuck with what might be a much higher value and a greater tax burden.