In her overview of the OECD Secretariat's "unified approach",  Zoe Andrews mentioned that a robust dispute prevention and resolution mechanism will be needed. 

Ease of administration is going to be important for market countries and multi-national enterprises alike. Achieving consensus and stability of the tax system will to some extent depend on the design of a well thought out administration framework and appropriate and reflexive dispute resolution mechanisms which meets the needs of a range of stakeholders.

The dispute risk under the “unified approach” arises primarily because of the potential overlap between the determination of Amounts A and C. It is conceivable to predict that such disputes could concern:

• the application of the “fixed return” methodology in circumstances where taxpayers or administrators dispute whether the deemed base line should apply having regard to what each stakeholder considers to be the level of marketing and distribution activities taking place in market jurisdictions; and/or
• double taxation arising from the application of the framework to the extent that profit under Amount A might be duplicated in Amount C and taxed in the market jurisdiction.

The challenge for the Secretariat and for the members of the Inclusive Framework on BEPS going forward is how to appropriately and reflexively design both 

• the framework to minimise the potential for disputes arising inherently from system design factors; and 
• effective dispute resolution mechanisms to prevent or resolve disputes early.