Depreciation depends largely on age, condition, and the current desirability of the property's features and location. Sales comparison models are usually more important in appeals. A sales comparison model says the estimated market value of your property equals the sale price of a comparable property, with adjustments to the sale price for differences between your property and the comparable. For example, if your property has a swimming pool and two bathrooms, but the comparable has no pool and three bathrooms, you would add the value of the pool to the comparable's sale price and subtract the value of a bathroom. The result would be evidence of what you might expect to sell your property for.
Assessors use more than one comparable, usually three to five.
Also, they use more complex models that incorporate many more factors. Every jurisdiction has an appeals process mandated by law. The first step is usually an informal meeting with someone in the assessor's office. Information on the mechanics and deadlines for setting up an appointment should be included with your assessment notice, along with similar information for the entire appeals process. During or before this informal meeting, you should review the property record form on your property to be sure all the information is correct.