The Multilateral Instrument (MLI), which is a result of the work done in Action 15 of BEPS, is a tremendous tool for a quick implementation of a number of BEPS measures in the worldwide treaty network. Action 6 (Treaty Abuse) provides as a minimum standard a mandatory obligation to introduce an anti-abuse clause in tax treaties, either by means of a so-called Principal Purpose Test clause (PPT), a Limitation of Benefits clause (LOB), or a PPT combined with a simplified LOB. Under the PPT, tax treaty benefits will be denied if the competent authority determines that a tax payer had “as one of its principal purposes” obtaining tax benefits under the treaty, based on all facts and circumstances. Is economic substance still enough? What about a business purpose? What facts and circumstances are relevant in this determination? What is the line between a purpose and a principal purpose? Do special anti-abuse rules (SAAR) prevent the application of the PPT ? How do the anti-abuse clauses in the Anti-Abuse Tax Directive and the Parent Subsidiary Directive interact with the PPT clause in the MLI? Are they different in scope and nature? As second distinct and separate topic, further to Action 14, the MLI offers the possibility to introduce in tax treaties an arbitration procedure to resolve conflicts. The panel will also deal with the questions arising from the arbitration procedure itself in the MLI, the potential future span of the arbitration and the interaction with other similar procedures already in place, for example the EU Tax Disputes Mechanisms Directive and the EU Multilateral Arbitration Convention.