With the advent of the European Union, tax harmonisation has become a key issue throughout Europe. Harmonisation by its nature involves the comparison of the different taxation systems that prevail in Europe. One obstacle to this comparison is the fact that each country describes its taxation system in its own language. Clearly, the translation of terms extracted from taxation systems is essential to mutual comprehension. However, language barriers, although significant, do not represent the only difficulty. Taxation systems in Europe have evolved from two main trends resulting in the Anglo-Saxon and the Latin taxation systems. Both types of system have developed separately over the last 200 years and each is based on different underlying concepts. Despite reform, these generic conceptual differences still apply in addition to the various socio-economic factors which have influenced the development of the taxation systems. Recognition and explanation of these difficulties is of paramount importance. This thesis discusses some of the terminological issues raised by conceptual non-equivalence and highlights ways in which terminology as a discipline is a useful tool in isolating these issues. This discussion occurs within the context of a comparison of two specific taxation systems (Spanish and Irish) from the perspective of the translation of Spanish terms into English. The investigation is structured as follows: an examination of terminology as a discipline, an outline of the structure of the Spanish and Irish taxation systems, a discussion of Spanish-English taxation translation difficulties and a Spanish-English glossary of terms.