Resumen.

The OECD Multilateral Instrument (MLI) introduced the principal purpose test (PPT) as a considerable step forward in counteracting treaty abuse. This article analyses the PPT rule in light of the possible restriction of EU freedoms. The first part analyses the wording, structure, rationale and effect of the PPT rule. Particular attention is paid to the reasonableness test and to the circumstance that the PPT rule introduced by the OECD MLI does not literally incorporate a reference to the genuine activity and the business purpose and, as such, seems to lower the threshold of abuse compared to the CJEU standard. Subsequently, compatibility with EU law is explored via the three-step process as developed under settled case law of the CJEU. An interim conclusion is reached concerning the risk of incompatibility of the PPT rule with EU law. Next, an interpretative effort is made on the basis of a systematic interpretation (1) of the Commentary on the OECD Model (2017) and (2) of recent CJEU case law in order to show that PPT rule may be reconciled with the CJEU standard of abuse and a compromise may be achieved. Finally, the achieved compromise is briefly exemplified having regard to an "quity wall" structure in order to illustrate a fact pattern (different from the clear-cut examples given by the OECD Commentary) that might fall within the scope of the PPT for tax treaty purposes.