There could be a few reasons that a home is not selling; price, presentation, location. But marketing is the number one reason a home doesn't sale. The tax value is very rarely a factor. Lenders rarely look at the tax value as a value indicator, that is what the appraiser is for. When a home is appropriately priced, it is actually a plus to find the tax value well below, indicating the taxes are not too high for the property. Of course, you have to consider whether the tax office has recently performed a recent valuation or if they are working on a value that could be as old as 7 years. Real value adjusts in real time while tax value is adjusted over many years. Hope this helps!