The article aimed to check company size's impact on the effective tax rate (ETR) in the Visegrad Group countries and Serbia. The research hypothesis suggested a positive relationship between company size and ETR, in line with the political power theory (PPT). This means that greater tax burdens are transferred to larger companies. The research hypothesis was verified with the use of regression models. The results indicate that in Poland, Slovakia, and Hungary, there was a negative correlation

more »

... tween company size and ETR. The conclusions are consistent with the political cost theory (PCT). This may indicate that in developing countries large companies have the tools to lower the tax burden. In 2018 and 2017, there was no statistically significant correlation between the size of the companies and ETR in the Czech Republic and Serbia. Additionally, it was noted that the companies from Hungary and Serbia use IFRS contributed to lowering the ETR.