When a comparable property has a feature the subject property does not, what must the appraiser do?

When a comparable property has a feature that the subject property does not, the appraiser must consider the impact of that feature on the value of the comparable. The correct approach is to adjust the value of the comparable property downwards to accurately reflect the differences between it and the subject property. This adjustment is essentially a way of "normalizing" the comparison.

By subtracting the value of the feature from the comparable's price, the appraiser aligns the comparable more closely with the subject property’s attributes. This method ensures that the appraisal reflects a more accurate market value for the subject property by taking into account how much the added feature of the comparable might contribute to its overall value.

The other options do not align with appraisal principles: increasing the value does not account for differences; ignoring the feature fails to provide a proper comparison; and assuming it has no value overlooks the potential market impact of the feature, which could mislead the valuation process. Overall, making a downward adjustment based on the absence of a feature is the most reliable method to ensure accurate and fair appraisals.