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or with another agency of government. Even where they are not (for example, in the United Kingdom), a fall-back option is available: street maps with a functioning street address system.

3.16 In developing countries, none of these can be relied upon. Some parcel maps may exist, but their coverage will be limited to higher income areas. Street maps may exist for lower income areas, but they do not a provide a basis for discovering properties not visible from the street. And street maps fail to provide a foolproof identification system. Systematic house numbering systems cannot be relied upon in most developing country cities.

3.17 Many developing countries--particularly in former British colonies-do not use map-based geographical referencing systems. Cities as large as Calcutta, Karachi, and Ibadan simply divide their territory into zones, assign each zone to an inspector, and assign him responsibility for discovering all taxable property in his jurisdiction. To provide the unique identifier, a tax identification number is painted directly onto each building.

3.18 In Calcutta and Karachi, the taxing authorities claim that this approach works, but the claim is difficult to verify. The system places much faith in the honesty of the inspectors--and in the willingness of taxpayers not to paint over their tax identification numbers. In some cases this faith is clearly misplaced; in Ibadan, Nigeria, so many taxpayers have painted over their tax identification numbers that most tax bills are undeliverable.

3.19 Some form of map that identifies parcel boundaries therefore appears necessary to ensure complete coverage and ineradicable identification. But there are many standards of mapping--variants in both the quantity and quality of information to be mapped, and widely differing costs associated with the different options. As maps can be major expense of starting up, the costs and benefits of different options need to evaluated carefully.

3.20 The standards required of a property tax map are modest. The map must simply enable the taxing authority to account for all the properties and identify each in a way that cannot be eradicated by the taxpayer. In principle, these basic requirements can be made with a map that is neither accurate in terms of scale, nor complete in the sense of including the entire boundaries of each parcel. As long as the map demarcates the point at which each parcel's boundary intersects the street--and all parcels front on a public street--this approach meets the requirement of comprehensiveness and ineradicability.

3.21 This approach is uncommon--in part, one suspects, because decisions about mapping standards are made by surveyors who have professional standards to uphold. The case for adding one characteristic--the boundary of the entire parcel--is, however, fairly persuasive. By mapping the whole parcel, the taxing authority can ensure that all the land is accounted for and can obtain data on the land area of each parcel, for later use in determining value. 3.22 Parcel boundaries need not be mapped with precision, however. The standards of accuracy that would apply to a legal demarcation of boundaries are inappropriate to a tax map. A tax map does not constitute recognition of a legal claim to property ownership. Precise boundaries therefore do not need to be determined on the ground, nor accurately represented to scale on a map.