State law in Alabama requires that 25% of all county properties be re-appraised every four years. There is simply not enough manpower to do that. As a result, the counties rely on artificial intelligence software to calculate the appraised values. Often, they are wildly wrong. If the tax appraisal is too high, the property owner protests and gets it corrected. If the tax appraisal is too low, the local government doesn't get the full amount of taxes they could, but when compared to the manpower costs to get accurate appraisals, it doesn't matter. If a tax appraisal is too low by $50,000, and if the property is owner occupied residential property, then it is assessed at 10% of its tax appraised value. The taxes might be around 5.5% of the assessed value. So, tax appraisal wrong by $50,000 makes the tax assessment wrong by $5,000, makes the tax bill too low by $275. It's just not enough money for the county to stress over.
As far as appraisals, the appraiser is allowed to used foreclosures and short sales as comparables if the market is primarily foreclosures and short sales. Here is an excerpt from Fannie Mae rules regarding appraisals and foreclosures:
"Use of Foreclosures and Short Sales
It is acceptable to use foreclosures and short sales as comparables if the appraiser believes they are the best and most appropriate sales available. The appraiser must address in the appraisal report the prevalence of such sales in the subject's neighborhood and the impact, if any, of such sales. The appraiser must identify and consider any differences from the subject property, such as the condition of the property and whether any stigma has been associated with it. The appraiser cannot assume it is equal to the subject property. For example, a foreclosure or short sale property may be in worse condition when compared to the subject property, especially if the subject property is new construction or was recently renovated. For appraisals that are required to be UAD compliant, the appraiser must identify the sale type as REO sale or Short sale, as appropriate. (For specific information regarding comparable sale adjustments, see B4-1.3-09, Adjustments to Comparable Sales, and for information regarding financing types, see Fannie Mae and Freddie Mac Uniform Appraisal Dataset Specification, Appendix D: Field-Specific Standardization Requirements). "