Due to the notification, the MLI will in principle have effect on the Swiss-Luxembourg treaty as of 1 January 2021. The wording of the treaty is yet to be published. However, it is currently expected that the revised Swiss-Luxembourg treaty will only incorporate changes pursuant to the choices made by Switzerland and Luxembourg under the MLI. This notably applies to the inclusion of the principal purpose test as a general anti-avoidance rule. With respect to Switzerland, the Swiss federal tax administration has constantly applied a general anti-avoidance rule under the current treaty and the MLI should therefore not substantially impact current practice in Switzerland. From a Luxembourg perspective, the principal purpose test will give more leeway to the authorities to challenge potential treaty abuse, but the changes to the treaty are otherwise not expected to have a significant impact. It is therefore recommended to review existing Swiss-Luxembourg investments in view of the revised treaty.