My understanding is they are based on actial real values.
And a few other things thrown in.. type/ number buildings, if subdividable, availability of services to do so around it, contours,etc
eg lets take a Sth Auckland suburb..
For many yrs (couple decades) was below auckland and nation value going on real sales numbers. Then this area becomes popular for investors , do uppers, and then under the unitary plan becomes able to subdivide down to 300 m. Has a tidy 3 bed house, large garage and shed. Suddenly it becomes close to the new Auckland ave.
Also worth to note the houses ( not the new units) are now selling , an have been for the last 12 months a little either side of GV.
What has happened because of investment, unitary plan changes, a complete change of balance has taken place with many low income area now taken huge jump in real sales value and other more " grammar zone areas not having that huge jump in actual sales value therefore taken a less of a rates increase.
Then go to somewhere on the Sth west edges of Auckland.. again these are selling over the last 12 months.. a little close either side of GV.
If thinking about appealing..I dont know how long after the new gv GVs came in.. that was Aug last yr, appeals are open till.
If want to do a little research on resent sales in your area an GVs you can use many current realator sites.. a good place to start maybe would be here.
Put the addy in at the top... go to , zoom in see recent sales GV s estimates of places around, description.
And if want more details of the property, rates, services etc the Auckland Council GIS..
We have kept a data base since 2002 of a large area of Sth Auckland that covers top end value down to full on bottom end rental.
And worth a note.. many jaffers complain about how much they pay in rates..without actually making a comparison with other areas of NZ.. even those with less or no services.
Want cheaper rates.. stay in Auckland..or at least in the more populated areas.
eg say a 1200 sqm section garaging , workshop, 3 bed solid house and a similar house, 800 m sq section similar garaging no storm water on the edges of Auckland have near the same rates.
Move over the boundary to the next council, the deeper you go the higher the rates with less services.