Council Tax Banding Calculation

PaulJJ1981

Hi
I have used the council tax band tips to see if my band is too high (currently F).  My neighbour's band is lower (E), but the house valuation tool shows different results depending on what dates I use.  Zoopla shows that my house has been sold twice since 1991 - once in 2005 & again in 2017 (when I bought it).  Between these dates the house was extended so therefore the house valuation increased, due to the larger size.  If I use the data for 2005 the band shows E, whereas 2017 shows F.  As the extension was built after 1991 should this valuation be disregarded?
Thanks  

lincroft1710

All HPIs are inaccurate, they can only give a rough guide to 1991 prices. Look at the bands of other houses in the area  similar to yours and see if you can make a case for a lower band if you find any in Band E.