The importance of tax and tax system for modern coutries is being explored by many authors in their books, remarking that the term „tax state“ is increasingly being used for the modern state. Within the tax system, income tax stands out as one of the most bountifully fiscal instruments for money collecting. Income tax roots come from distant history and as many times as income tax was abolished so many times was it returned back into tax system. The Republic of Croatia, although a relatively young country, has also included income tax within its tax system. Income tax was changed several times throughout Croatia's short history but its essence has always remained the same – collecting revenue for public finance needs. With the major financial crisis arrival, came employment decrease and a difficult situation in the economy and income taxation came to the center of attention, precisely the fair distribution of tax burden. All the Europion Union members, which Croatia is also a member of, were in a similar situation, but they have been more successful in dealing with the crisis and embarking on economical recovery. A good example is the Republic of Ireland which is similar to Croatia in territory area and population number, but in development far ahead. This has been recognized by many young people in Croatia, especially in Slavonia, who have been forced by the difficult economic and political situation to migrate and settle in Ireland. The main assumption of this graduate paper is the fact that the Irish tax system, precisely its income tax, burdens taxpayers in Ireland a lot less and that this is one of the reasons for such a large migration of Croats to that country. After defining taxation terminology related to personal income tax, its features and forms and its historical development has been presented, then the current taxation system in both countries was explored and presented with the purpose to confirm the inital assumption. Based on conducted research, for the purpose of calculating the annual tax liability for the same gross salary, both in Croatia and Ireland, a fictional case of taxpayer was presented. It was concluded that the assumption was correct and that the Irish taxpayer deducts a much lower amount of tax from his income than Croatian taxpayer and thereby realizes higher net salary than a person in Croatia