Residential vs Commercial Tax Rates in Chattanooga, TN

[John Tilstra]

Quick question for my fellow BP REI folks in Chattanooga, TN!

We are doing our due diligence on a duplex we're under contract to purchase in Chattanooga (Brainard), TN.  The most recent tax assessment/appraisal was in 2015, and noted the property was a duplex, but categorized it as "residential" property.  This means taxes are assessed on 25% of the property's appraised value.  (i.e. property appraises for $100k, you're taxed on $25k at country/city rates of 2.3/2.8%, and total taxes of $1279.)

However, according to the Hamilton Country tax assessor website states, "Industrial and Commercial Property assessed at 40 percent of value, and includes residential buildings with two or more rental units."

So, wouldn't this definition imply that duplexes should be assessed as commercial property and therefore be subject to paying taxes on 40% their appraised value?  If so, why was the duplex we're looking at categorized in 2015 as a residential vice commercial property?  (In 2015, both units were occupied, neither by the owner.)  

The difference in annual taxes is significant (about $750), so I'd love to plumb the depths of the collective BP brain.

Thanks in advance, and if you're in Chattanooga, hopefully we'll get to see you when we're back in the States this summer.