The constitutional limitations on the power of the states to tax foreign corporations present many intricate questions. In general it may be said that a state may tax foreign corporations the same as it may tax domestic corporations, but subject to the limitations found in the commerce clause and the Fourteenth Amendment of the Federal Constitution. The commerce cause takes certain subjects out of the realm of state taxation altogether. The state cannot directly impose a burden of any sort upon interstate commerce. It cannot even lay an excise on the privilege of doing intrastate business if the basis includes the value of the company's interstate business. The Fourteenth Amendment both limits the basis and the amount of the tax. It prevents the state from taxing property that is not in the jurisdiction; it also requires that every tax be fair as to amount.