According to the fair taxation principle, tax rates on income from savings should be similar to those on other income. In practice, they are lower. Different EU member countries have a different approach towards taxation of income from bank deposits and bonds. These differences, especially under the conditions of the developing single European market, have given rise to increased harmful competition between the member countries. This has disturbed the functioning of the single market, and had an adverse effect on rational allocation of capital. Attempts have therefore been made for several years to harmonize the principles for of savings income taxation. In spite of a certain progress, no common stance has been attained so far. The difficulties result primarily from the conflicting interests of the member countries. As the negative effects of tax competition become more and more palpable, the harmonizing efforts can be expected to gather momentum, especially with the common currency now in place. Harmonization work is also under way within the framework of the OECD. At present, Poland is under no obligation to introduce a tax on income from bank deposits and bonds, but the advent of such a tax seems inevitable in the future. Before it is launched, careful consideration must be given to the particulars: the date it becomes effective, possible exclusion of part of the savings income, and last but not least, the rate at which the tax applies.