Never, ever understood this.
The 5 Door DSG version has a higher CO2 output than the 3 door which pushes it into the next tax bracket. Fair enough you would think, the 5 doors obviously add a bit of weight and therefore push the CO2 up. However if you check the manual versions of the GTD, both 3 and 5 doors are exactly the same CO2 output, and even more bizarrely, if you look at the GTI, it doesn't affect the groupings all be it manual or DSG, the 3 and 5 door versions are exactly the same ?
For example:
GTI - 139g Manual - the same for 3 door and 5 door - VED Band E
GTI - 148g DSG - the same for 3 door and 5 door - VED Band F
GTD - 109g Manual - the same for 3 door and 5 door - VED Band B
GTD - 119g DSG - 3 door only - VED Band C
GTD - 122g DSG - 5 door only - VED Band D
WTF ?