While much ink has been spilled on the primacy of EU law, many of its features still remain underexplored. Leaving aside the ubiquitous struggle over primacy’s absolute character for a moment, this article takes a deep dive into primacy’s effects on the daily work of domestic judges. We analyse, systematize and rethink the steps that they are supposed to take after finding that national law conflicts with EU law. In a first step, primacy requires them to disapply the respective national provision (primacy’s negative effect). A recent line of cases goes even further, suggesting that judges might not only be obliged to disapply, but even to invalidate national law. This contribution sheds some light on these developments and assesses their risks and added value. Second, the act of disapplying national law may create a problematic legal vacuum in the domestic legislative framework. Therefore, national judges are increasingly reaching out to the Court of Justice, asking to avoid such gaps by limiting primacy’s temporal effects. Yet, in the absence of such suspension, the domestic judges will need to take the positive step of filling the vacuum (primacy’s positive effects). This article provides a novel systematization of the various situations with which domestic judges may be confronted, showing how ever more legal ingenuity and judicial creativity are required. Finally, the article demonstrates how these requirements may create tensions with fundamental principles of domestic constitutional law, such as the separation of power, the judicial architecture and legal certainty.