Taxes will fulfil their function in economy adequately when and only they are in conformity with the principles of a market economy, and in particular with the freedom of economic activity and free competition rules. Therefore the implementation of external elements such as taxes into the economic mechanism must be properly integrated with that mechanism. On the microeconomic scale, taxation rules should, above all, conform with the principle of the ability of a tax payer to perform the obligation, i.e. the subjects on whom the tax obligation has been imposed must be capable of fulfilling that obligation. Further, the influence of national economies must be recognised, which is of particular significance in the European Union where tax harmonisarion is one of the key elements of the overall harmonisation of laws of its member states. From the legal aspect, the tying of taxes to economy manifests itself mainly in the relations between tax law and civil law. A reasonable legislator should attempt to ensure a compromise between the interest of the State Treasury and the cohesion and completeness of the legal system ensuring that institutions formed and regulated according to the procedures of the civil law code can function in a manner not disrupted or hindered by tax law. In the exercising the objectives of the legislation policy and selecting legislative techniques, it is necessary to account for the fact that tax law operates within an area of natural economic activities phenomena and that the legal regulations must be very precise and clear. Another important element of proper legislation procedure is accounting for potential conflicts of interests of different groups subjected to a given legislation, and providing for compromises to alleviate their such potential conflicts.