[mcv]

That's why I think you need to tie it in a non-transferable way to a market. So if Amazon UK pays Amazon US for a license, either it pays that license in the US, which means they can't deduct it from their UK profits, or they pay the license in the UK, which means Amazon US has to pay taxes on it in the UK. Either way, someone is going to pay tax over that revenue in the UK, and it'd be the most profitable for Amazon if it was done by the company that also spends the most on costs (labour, services, whatever) in the UK.

I still think that would actually close these loopholes. It would erect some barriers to international trade, though, because companies making their costs and revenue in the same market have an advantage over companies coming from other markets. I don't think that's necessarily bad, though, and it can be mitigated by trade deals by which countries decide to treat their markets as a single market for these purposes as long as their tax rates are similar enough. Of course then they shouldn't make those deals with tax havens, and they'd be stupid to do so, because they'd be inviting a loss in tax revenue if they did that.