A sound property tax is based upon an accurate and fair valuation system. The property valuation system in Taiwan has over these years evolved into a sophisticated one. Accuracy and equity of this system has however up to date seldom been under scrutiny. To accomplish a speedy valuation for taxation purposes, all properties in Taiwan are assigned into a number of valuation zones. Properties in the same zone are similar in their value, site size and neighbourhood amenities. This paper sets up to examine the performance of property assessment in a selected group of valuation zones in Taipei City. The emphasis is placed upon the vertical inequity within a valuation zone and horizontal inequity among valuation zones. We also employ a well-established equalization procedure, Vertical Horizontal Appraisal Adjustment System, to correct for the identified inequity. In addition, the spatial element of assessment inequity is also looked into. Zones where properties are over- or under- assessed are often found to locate close to each other. Clustering of unfairly-assessed valuation zones itself represents another type of assessment inequity. We finally propose a number of potential explanations for the observed assessment inequity and possible cures.