The less they tax corporations the more the burden will fall on income tax. These big multinationals have been defrauding countries worldwide for decades. The issue is at the core of the political turmoil we are experiencing.
I'd like to know how much less income tax would be, if we could tax multinationals properly.
The income tax would be less but so would be your salary. The corporate tax is another cost for the company.
The tax avoidance schemes used by most major US companies are to avoid US taxes on foreign income. Most developed countries have territorial tax systems so their companies do not even need to use these fancy legal maneuvers because the income is largely exempt anyways.
In any given year corporate income tax is like 6-10% of federal receipts so even if that was doubled there would not be a huge decline in income taxes needed. The way the US does corporate tax is really also not that great from an economic perspective because it is a form of double taxation. The Estonian model of only taxing distributions incentivizes investment and avoids many debates over depreciation etc.