Multinational Companies’ taxable income and Tax Fairness -Focusing on Apportionment Formula and Filing Unit of U.S. State Corporate Tax and OECD Digital Tax

With respect to the tax strategy of Multinational Enterprises (“MNEs”) which has utilized price-transfer and retained earnings to avoid tax liability, this study analyzed whether unitary group as a tax filing unit and apportionment formula to combined taxable income could prevent MNEs from avoiding tax liability using base erosion and profit shifting (“BEPS”). MNEs have performed across border activities. MNEs incorporated subsidiaries in low-tax jurisdiction and retained the earnings as possible as they can. Although high-tax jurisdiction where economic activities have taken place and value has been generated is entitled to tax the profit of MNEs, current rules have not provided high-tax jurisdictions with appropriate tax assessment for more than dozens of years. This study analyzed U.S. exemplary cases related to unitary group taxation subject to consolidated accounting of OECD Pillar One and U.S. state corporate tax. The study analyzed the characteristics of apportionment formula factors and revealed why sales factors is dominant among them. Several examples with and without intercompany transactions clearly demonstrate that taxing methodology of combined group filing and apportionment formula of taxable income can eliminate tax avoidance of tax liability using BEPS by MNEs. Therefore, the methodology of tax return filing is able to replace arm's length principle used for international tax audit skill which has a lot of controversy over consistency, objectivity, and efficiency. Due to different background among jurisdictions, uniformed codes can cause reverse effects against OECD Pillar One and Two. Heading for a soft landing toward apportionment formula, combined income’s fair apportionment among nations is one of the first and pivotal challenge because some formula would be favorable for some nations but, would be unfavorable for some others. To implement the methodology of unitary group filing and apportionment formula, at this point, it can be utilized as one of tax auditing approach. To solve the conflict of interests through convincing reasoning, there must be theoretical researches on apportionment formula, apportionment factor, and filing unit.