I agree that this is hard and that there are no global tax authorities, I wasn't trying to say that's something that can just be implemented. It's probably the most realistic solution to the transfer pricing problem though, which probably says something about the scale of this issue.

I also disagree that the developing world is that much of a problem. Currently, in the developing world, money flows to places like the U.S. Virgin Islands, Bermuda, etc. While I'm sure they are not the only places that could act like as tax havens, there's probably a limit. Multinationals probably aren't going to want to relocate their headquarters to a developing country like Egypt for a variety of reasons like language, currency, corruption, weaker property laws, ease of moving cash, etc. Tax havens could also be disabled with tools like sanctions on a G7 or G20 basis. Bermuda doesn't want to play ball? Sure, then the G20 banks and governments will not allow their citizens to deal with Bermuda.

As other people have said, the goal isn't to prevent this from happening, it's to make it too risky or expensive to justify as opposed to just paying corporate tax on profits without shifting them.

It’s like fixing bugs in software: I don’t expect any given proposal to solve everything or to close every loophole and workaround, but it’s still important to put continuous effort into trying.

> Nobody is going to enforce these things

It doesn’t become effective until the G20, or at least G7, pass it. Part of the law would be automatic tariffs against non-participants. That leaves non-signatories with a choice between compliance and economic decimation.

G7 can say: no more trade on our soil if you don't pay the minimum tax.

The US would sanction them, and then they'd be screwed.

Why don’t countries do this already? E.g., most European countries and presumably the US dislike that Ireland undercuts corp tax, so why don’t they penalize corporations who operate in their borders but are headquartered in a country that doesn’t have agreeable tax laws?

Well they sometimes do (e.g. fine them) but at a scale where it matters these are companies that also have leverage - if Amazon responded 'Ehhh we might stop delivering to the UK then, Brexit is already an expense, with this too ...' and then the Government is the government that lost/banned/there-is-no-good-spin Amazon.

Within the EU, (or EEA perhaps) I vaguely recall there's some restriction against penalising for things like this, as long as the other nation is also a member state. (Since viewed as a whole, 'one EU', it should be fine, I suppose.) Struggling for the right words ro search though.