This article analyses profit shifting from the Polish economy and proposes a methodology for quantifying its magnitude and fiscal effects. Adopting a microeconomic perspective, the study draws on firm-level fiscal and financial data for companies registered in Poland and applies microeconometric methods. The obtained results reveal that foreign multinational subsidiaries exhibit significantly lower average tax profitability than domestic standalones (i.e. Polish-owned companies with a simple ownership structures), indicating profit shifting out of Poland. The most reliable quantification estimates suggest that foreign subsidiaries transfer roughly one-fifth of their profits abroad, thereby reducing the tax base and leading to a loss of tax revenues by around 2.6 billion PLN annually—equivalent to approximately 6.4 percent of CIT revenues in Poland between 2011 and 2021. Given the empirical strategy employed, this estimate should be considered conservative.