The aim of the paper is to define the effects of fiscal aspects that determine the behaviour of economic agents (especially firms and households) in the Czech Republic and Poland and to define the side effects that occur as a result of these fiscal aspects. In a global comparison, the two countries analysed show similarities in terms of labour costs and VAT, i.e. the aspects that primarily influence the motivation of firms to continue doing business in a given country. Both countries analysed are export-oriented and their fiscal policies show similar features that do not cause major spillover effects. In the short run, however, there are situations where temporary changes in the fiscal policy of one or the other country lead to spillover effects in the form of changes in the purchasing behaviour of economic agents, especially households.