836. To remove treaty obstacles and implement the four elements discussed in the previous section, the method used must ensure coordination, consistency and certainty, and operate in a speedy manner. The best way to do this would be through a new multilateral convention.
837. The Inclusive Framework initially considered using the Multilateral Convention to Implement Tax Treaty Related Measures to Prevent Base Erosion and Profit Shifting (MLI)2 (or creating another instrument that works in the same way to modify existing tax treaties) to implement Pillar One, but ultimately agreed that it would not be a suitable instrument: implementing measures that need to be part of a multilateral framework would not always be feasible (e.g. multilateral dispute resolution mechanisms) nor would implementing changes and measures between jurisdictions that do not have a bilateral tax treaty be possible (e.g. the dispute prevention and resolution processes for Amount A).
838. As bilateral tax treaties would remain in force and continue to govern cross-border taxation outside Amount A, a new multilateral convention would need to coexist with the existing tax treaty network and, for its parts on the determination of Amount A tax and elimination of double taxation, supersede and prevail over existing bilateral tax treaties for the taxation of in-scope MNEs. Further work will also be required on the relationship of the multilateral convention with bilateral tax treaties concluded after its entry into force (see paragraph 852).
839. The new multilateral convention would thus operate differently than the MLI, which was used to directly modify existing provisions in tax treaties. The new multilateral convention would provide a multilateral framework to facilitate the coordinated and effective implementation that is necessary between multiple jurisdictions and would, for its parts on the determination of Amount A tax and elimination of double taxation, supersede all bilateral tax treaties in force.
840. As noted above, there would not be treaty barriers that would need to be removed between jurisdictions that currently do not have a treaty with respect to those parts and those jurisdictions could rely on their domestic legislation to apply and administer Amount A. The part of the multilateral convention that would implement the features of the new simplified administration process and the tax certainty-related processes would apply to all parties and would also close the gaps in treaty coverage. That part would also make the appropriate linkages for all signatories to the rules that govern the application and operation of Amount A.
841. If developing a multilateral convention is the ideal way to ensure a legal obligation to apply and administer Amount A in the same way, and better coordination and speedier international public law implementation. However, some jurisdictions may need to explore whether they could exceptionally make all necessary treaty changes by amendments to their existing bilateral treaties and domestic law within a reasonable timeframe. Under such an approach, a jurisdiction may be able to agree with its treaty partners to bilaterally amend its existing treaties to remove obstacles for the determination of Amount A tax and elimination of double taxation and then rely on its domestic legislation to apply and administer Amount A. Allowing a jurisdiction to require a bilateral approach would, however, place an additional burden on partner jurisdictions who would be required to implement on both a bilateral and a multilateral basis. Also, it is not clear that the multilateral dispute prevention process for Amount A could be implemented other than by a multilateral convention given the need to coordinate results among multiple jurisdictions.
842. As part of this work on possible bilateral amendments to treaties, further thoughts could be given on the development of a separate instrument that would deal with the features of the new simplified administration process and the tax certainty-related processes.