If the earnings are attributed to the country of evasion, and it is secretive as they all always are, how does the country of residence even know or prove how much they need to tax. The pandora papers would not be so revealing if it wasn’t for the secrecy part.

They can add a new rate for products sold by companies in non-signing countries.

"Paying" £1,000,000 for intellectual property in the virgin islands? There's a 12.5% tax on that, not VAT, so no, you can't offset it, thanks!

The money is coming out of non-secretive countries, right? Eg. by end user credit cards o by 3rd companies buying ads or data.