The present analysis investigates the rationale for delegation to domestic institutions in the EU. This issue is prominent in merger control, where the Commission can refer the assessment of concentrations between undertakings to national competition authorities. We argue that the purpose of referrals is to reduce the decision-making costs. Employing data from 2004 to 2012, we show that the recourse to national authorities is associated with taking advantage of agency expertise and shifting the blame for policy failures. Conversely, referrals are not grounded on the need to reduce the number of pending cases. These results hold when controlling for confounding factors such as the involvement of non-EU countries, the different commissioners for competition, and sensitive economic sectors.