> It's not so much that it's hard, it's that it has a lower return on investment, because the IRS gets money from finding mistakes or intentional fraud....
Isn't this exactly what all megacorps are hoping for everyone thinks? I am not saying that you are wrong but these megacorps are some of the most evil the Civilization has ever seen (see Meta) and now you and I are hired as tax attorneys - pretty soon (if not right away) one of us will go "this shit's very much so illegal but who is actually going to audit us? - the answer, per your comment is basically no one because we think these megacorps and their lawyers are there to play by the book...
In order for that to make sense to them, it would have to be impossible for them to avoid paying taxes without breaking the law, but the very nature of applying "corporate income tax" to an international supply chain makes that relatively straightforward.
The general problem is this. You have a company with its headquarters in Ireland that designs a product in California, manufactures it in China and sells it in Germany. In which country did they make a profit and therefore owe taxes? It depends on what each subsidiary bought from the others and how much they paid, so they're going to structure their operations so that the profit ends up in the one with the lowest taxes. That's the defect in "corporate income tax" for international companies, and why it gives international companies an advantage over domestic ones.
In order to fix that you need a tax code that says the taxes have to be paid to the country where whatever subset of their operations you want to tax is actually present. But then it's not "corporate income tax" anymore. If you want to tax them in the location they have workers it's payroll tax, if it's where they have buildings it's property tax, if it's where they have customers it's VAT, etc. You need it to be something they can't so easily move out of your jurisdiction. Because if you say that it's profit then they'll just arrange to make their profits in Ireland or Bermuda.