To determine if an assessment is fair, sales in the immediate neighborhood that are comparable in elements of comparison (for example: style, design/appeal, square footage, age, condition, lot size, etc) need to be identified and analyzed.
The town's sales books (see related links) by village list valid arms length sales to consider. Market value is what a home should sell for under normal conditions. This excludes sales whereby a buyer or seller is under pressure to act, possibly as a result of financial distress, relocation, death in the family, divorce, or similar reasons.
Determining market value is an art, not a science; however, the results can be relatively accurate if the right methods are applied and important details are considered.
Unfortunately, finding an "exact" comparable sale is rare. To account for these differences, the sales prices of the comparables need to be adjusted. This requires an analysis to determine if these differences would increase or decrease the sales price and by how much. The adjusted prices of the comparable sales would then be used to the estimate what the subject property would have sold for if all the characteristics were the same. This is similar to the analysis done by an appraiser.
The New York State Department of Tax and Finance has an excellent webpage on How to Estimate the Market Value of Your Home. In it they give an example of how comparable sales would be adjusted for different elements of comparison to arrive at a market value estimate.
The New York State Department of Tax and Finance has an excellent webpage on Reassessments. In it they explain that if your assessment increases, it does not mean that your taxes will automatically will increase.
NYS further explains:
Your taxes may increase, decrease or stay the same.
Market values of properties can increase, decrease or stay the same. The reassessment will ensure that your property is assessed based on current market values.
If your assessment does increase, it doesn't mean that your taxes will automatically increase. If the increase in your assessment is less than the average increase, your taxes will actually decrease. For example:
Reassessments don't increase taxes collected by local governments
The assessor is not responsible for taxes - only for assessments.
Months after assessments are finalized by the assessor, school districts, cities, towns and counties determine their tax levies - how much they need to collect in taxes.
The property tax levy is determined separately from the assessments. The tax levy is then distributed over all taxable assessments.
If assessments increase, tax rates should go down proportionally. This is because the tax levy is now being distributed over a broader tax base. If tax rates go up or stay the same, it simply means that the municipality or school district is collecting more in taxes.