Land is the dominant base on which property is recurrently taxed in Australia. If the taxation of land is to be sustainable, then the value of land must be determined in a simple and transparent manner. This thesis explores the complexity of valuing land for taxation purposes, in particular, in highly urbanized locations where vacant land transactions are rare. The thesis proposes that land should be valued for taxation purposes on the basis that it is used for its highest and best use. In the case of non-vacant land the added value of improvements may be deduced by reference to their cost. That is, the thesis argues that cost and added value of improvements are identical or at least similar where the productivity of the land is maximized. The thesis uses a mixed methodology design drawing on both the quantitative and qualitative paradigms. The methods are conducted sequentially with one informing the other and include simulations, a survey and focus groups. The thesis demonstrates that the neutrality of land as a tax base is dependent on its value being determined on highest and best use, and that consistency in the valuation of land impacts on the neutrality of the tax. That is, neutrality is best achieved where the value excludes improvements that are not maximally productive, and which therefore may distort the value of the land, and where maximally productive improvements are consistently accounted for in the valuation of land. Further, the thesis demonstrates that the valuation of land for the purposes of taxation is a manufactured process. The process needs to be codified to meet the principles of good tax design and specifically the principles of simplicity and transparency. In summary, the absence of a consistent method of valuing land in highly urbanized locations needs to be addressed through the use of a codified framework which firstly determines the highest and best use of land, and then partitions land from improved value. The thesis concludes that while land is argued to be a neutral base for taxation purposes, it is its highest and best use that is the specific factor in assessing its neutrality in highly urbanized locations. It is concluded that neutrality is absent in all other bases of value used to assess tax on land.