There's already an established principle of double taxation treaties between countries so worst case the company would pay max((country.tax_rate for country in

There's already an established principle of double taxation treaties between countries so worst case the company would pay max((country.tax_rate for country in company.operating_countries)). It's also worth noting that there has been and is a strong effort to harmonize accounting across countries (eg GAAP). Countries might tax differently but that really doesn't matter since you're just slicing up the same pie differently. Don't get me wrong: this isn't simple. For one thing, once a company likes Apple gets into a position of choosing how to divide up $20B in taxes between countries, this gives them a lot of power. Countries will try and incentivize them to pay taxes to them instead of someone else. Again there is precedent for this sort of thing and arrangements can be treated by the like of the EU or even the WTO as unfair tax subsidies. But it could get complicated. Like what if Ireland decides to exempt Apple from sales taxes and the UK decides to exempt Apple from payroll taxes to incentivize them to pay taxes their instead of somewhere else? This is one reason why it'd be important to, at the same time, establish a minimum baseline for what taxes a multinational owes in each jurisdiction. The fact that a company can do billions of pounds in business in the UK and report all that income Ireland thus paying a few million pounds in taxes each year is ridiculous. How about this for an idea: establish how much revenue comes from each country based on the source so if someone in UK hands you money then that money is attributed to the UK. Divide that by total global revenue and then at least that percentage of profit has to be taxed in that counry.