Die Dis cus si on Pape rs die nen einer mög lichst schnel len Ver brei tung von neue ren For schungs arbei ten des ZEW. Die Bei trä ge lie gen in allei ni ger Ver ant wor tung der Auto ren und stel len nicht not wen di ger wei se die Mei nung des ZEW dar.Dis cus si on Papers are inten ded to make results of ZEW research prompt ly avai la ble to other eco no mists in order to encou ra ge dis cus si on and sug gesti ons for revi si ons. The aut hors are sole ly respon si ble for the con tents which do not neces sa ri ly repre sent the opi ni on of the ZEW. The issue of base erosion and profit shifting has been on the international policy agenda for several years now. The aim of this paper is to examine how firms adjust their profit shifting mechanisms in a changing institutional environment. In particular, we test whether firms substitute one profit shifting strategy for another if respective costs change. To this end, we exploit changes in the strictness of transfer pricing regulations and thin capitalization rules over time in a panel of European multinational firms and study a quasi-experimental reform setting in France. We confirm existing evidence that tightening transfer pricing regulations reduces the tax sensitivity of earnings before interest and taxes (EBIT) substantially. Our results show, however, that this reduction includes both a reduction in profit shifting activity via the transfer pricing channel and a substitution with debt shifting. Moreover, firms using debt shifting to begin with rely more heavily on tax optimization of transfer prices when thin capitalization rules are strengthened. If transfer pricing regulations are also strict, the conditional reform effects show that the substitutive response is more pronounced for a subsample of firms with a high share of intangible property (IP). The difference-in-difference approach for the French tax reform illustrates an increase in profit shifting based on transfer prices for treated firms facing new restrictions on debt shifting. Again, the effect is stronger for IP intensive firms.