First, contact your Assessor to find out how they valued your property. You may provide them with any evidence supporting your claim to value. The best evidence is an independent appraisal by a NYS certified Appraiser. You may also provide the Assessor with properties you feel are comparable to yours. These properties should be in your town, in a similar neighborhood and preferably have recent arms-length sales on them.
If you provide this information to your Assessor but still do not agree with the result, you may attend Grievance (link is external) to bring your evidence before an independent Board of Assessment Review comprised of individuals who reside in your town. They will take the evidence and make a determination. If you still do not agree with the outcome, you may go to Small Claims Court (link is external) to have the assessment dispute addressed.