The use of the tax on income by both the states and the federal government, and especially the heavy reliance of the latter on this source of revenue, has focused attention on the need for some form of coordination in this field of taxation. Both the states and the federal government have a legal right to tax income, but there is criticism of the overlapping taxation that exists between the federal government and the states and among the individual states. The criticisms of this dual taxation are: the cost of compliance has been increased; tax evasion and avoidance have resulted because of the nonuniformity of state tax laws; the states have resorted to tax competition; the cost of administration has become excessive; and conflicting tax laws have resulted in unequal taxation. In recent years the tax on income has become the most important single source of federal revenue. In 1947, for example, the tax on personal and corporation income yielded nearly 68 per cent of total federal tax collections, exclusive of payroll taxes.' To the states this same year income taxes accounted for about 15 per cent of total tax collections, exclusive of payroll taxes.2 The importance of the tax on income to those states which levy such a tax varies. In 1947 the tax on income, both corporate and personal, accounted for 40 per cent of total tax collections in Wisconsin, exclusive of payroll taxes.3 In Arkansas the percentage was about 8 while in Utah and Kentucky the income tax accounted for approximately 15 per cent of total tax collections.4 In general the southern states and the states west of the Mississippi received smaller amounts from the tax on income than did the northern states. The tax on income also represented a smaller percentage of total tax collections. Both federal and state income taxes produced a revenue of over $26,000,000,000 in 1947; of this amount the states received about 3? per cent while the remainder was taken by the federal government. The states have not developed this field of taxation probably because of the fear of interstate competition and the fact that the federal government has been taking such a large share since 1913.