> this type of property is notoriously easy to hide!

Not if you want it to be protected by a patent, trademark, or copyright.

IP offshoring is a big tax avoidance strategy already. Not that it couldn't be made harder to exploit, but it's not a fait accompli to simply tax the IP resident in a country.

You tax it at the point of enforcement. If someone wants to avoid paying the tax, then everybody gets to copy their stuff for free. It seems straightforward to me.

Sure, because we don't have an asset tax. If we had an asset tax, you'd have to register your IP. If you don't register your IP, you don't get protection. Not too different from real estate; if you don't have title, you don't own it.

I haven't considered all the economic consequences of this, but it does seem like enforcement is a minor problem.