From an Exxon-Mobil (EM) tax attorney:

Finally got a chance to pull the 10-K.

It is easy to confuse revenue with income before taxes. No one pays taxes on revenue. So when one says "Exxon paid a very modest U.S. tax rate of 6.4% of its income before taxes" it is calculating the amount on revenue. Before one determines what one's income is you subtract all your costs and other deductions. That gives you a net income number before taxes. Corporate taxes are done basically like individual taxes just at higher rates.

total revenue $404,552 billion
total costs/other deductions $334,078 billion
net income before taxes $70,474 billion

According to EM's 10-K they paid $29,864 billion in federal income taxes alone.

That does not include state taxes, franchise taxes, severance taxes, sales and use taxes. The effective income tax rate is 44%. This means that EM paid 44% of their net income of $70,474 billion to the US government.

Some might say "Since EM is getting its oil from foreign holdings at a cost that is a small percentage of the market price, the foreign taxes paid to the countries owning the oil seems arguably justifiable."

What people forget is how much money is invested UPFRONT before oil companies find the oil (if they are lucky).

EM does not include taxes that it collects on behalf of governments. The tax burden included is only the amount ExxonMobil pays not amounts withheld on others behalf.

Some might think that little U.S. tax is paid because many profits are attributed to overseas operations; so that even though EM is a U.S. company, US tax laws don't require payment of taxes on profits of overseas operations. Obviously, it pays the companies to have their accountants set things up so that as much as possible of operations are set up overseas in places with low income tax rates."

The U.S. tax system taxes on a world-wide basis that includes ALL revenue from EM overseas operations. This is very different from most European countries (except UK) that only tax on income generated in their own territory. US based companies have complained for years that this puts them at an unfair advantage to foreign companies. Foreign companies making income in the US only pay US tax on the income generated in the US (not what is generated outside of the US). That is why several large pharmaceutical companies home offices are in foreign jurisdictions like the Caymans or Bahamas so they can avoid US tax. A few years ago a lot of
hub bub was made about companies "outbounding" or "expatriating" causing Congress to change the laws and require a huge exit tax if companies leave the US.

For purposes of full disclosure, what is allowed is a foreign tax credit. So if you pay taxes in a foreign country EM is allowed to offset its US income up to 35% (US corporate tax rate) by the amount of taxes it paid on the income already.

The theory is that a company shouldn't pay taxes on their income twice. However, what you find is that for example, in Norway you pay 78% tax on $100 earned. In the US you can take a credit for only 35% so you subtract $35 from the $100 of income instead of $78 which is what the real cost was. There are also very convoluted rules regarding what type of income can be offset with credits. For example, you can't offset extractive income (getting oil out of the ground) with non-extractive (refining). As you can imagine most foreign taxes are paid
on the oil (extractive income) but we make an awful lot of money on the non-extractive side (transportation, refining, chemicals,) which can't take advantage of the taxes paid on the oil.