CRA indicates that the Treaty does not fetter the right of the US to impose GILTI tax with reference to Canadian subs’ income

The new rules on tax on “global low-taxed intangible income” or “GILTI” in s. 951A of the Code may result in a U.S. corporation being subject to tax on a current basis on active business income earned by a controlled Canadian subsidiary, even if that subsidiary does not have a permanent establishment in the U.S. CRA does not consider that this is contrary to Art. 29 of the Canada-U.S. Treaty, which confirms the rights of the US to impose tax on its own residents, subject to limited exceptions which are inapplicable here.

Neal Armstrong. Summary of 16 May 2018 IFA Roundtable, Q.1 under Treaties – Income Tax Conventions - Art. 29.