The Preamble of the Spanish Financial Transactions Tax Law establishes that “[t]he shaping of the tax follows the line taken by our neighbouring countries, including France and Italy, thus contributing to greater coordination of these taxes across Europe.” In this sense, the Spanish tax shows important similarities with those established in France and Italy in relation to the levy on the acquisition of certain shares and securities representing the capital of a company for consideration. Nevertheless, both the French and the Italian taxes apply to other types of transactions, not covered by the Spanish Law, which is why it is necessary to carry out the corresponding comparative study. Furthermore, the effects that have arisen from the application of this kind of taxes to financial transactions merited a proper analysis in order to determine if the main goals pursued by these taxes have been achieved in an efficient way. In any case, there are emerging tax challenges in financial markets connected, on the one hand, to the use of crypto-assets and distributed ledger technology, and, on the other hand, to the implementation of artificial intelligence and machine learning and the fair taxation of these operations. In this sense, the Spanish tax presents important similarities with those established in France and Italy in relation to the levy of acquisition for consideration of certain shares and securities representing the capital of a company. Nevertheless, both the French and the Italian taxes subject other types of transactions, out of scope of the Spanish Law, which is why it is necessary to carry out the corresponding comparative study. Furthermore, the effects that have arisen from the application of this kind of taxes on financial transactions merited a proper analysis in order to determine if the main goals persuaded by theses taxes have been achieved in an efficient way. In any case, there are emerging tax challenges in financial markets connected, by the one hand, to the use of crypto-assets and distributed ledger technology; by the other one, to the implementation of artificial intelligence and machine-learning and the fair taxation of these operations.