On September 21, 2007, Canada and the United States signed a Protocol agreeing to significant amendments to the Canada-U.S. Tax Treaty. The Protocol will come into force once ratified by both governments. If ratified in 2007, it will come into force generally as of January 1, 2008.

While key elements of the proposed amendments have been broadcast for some time (elimination of cross-border withholding tax on interest and extension of treaty benefits to U.S. LLCs, for example), the Protocol will implement additional, far-reaching changes in the context of cross-border structures.