Multinational firms will have to pay that level of tax on all of the profits they make worldwide, regardless of where the profits are generated.
If I have understood correctly from the article, this tax seems to apply to profits instead of revenue. If that is the case then all this does is justify companies hiring 10 more accountants and lawyers to find more novel ways to launder real corporate profit from exploitation into personal profit. Publicly traded companies might take a small hit to their next annual reports, but private businesses will experience almost no effect at all.
If a company has bought and "loaned" or given their executives cars, phones, food and rent stipends, paid for lavish parties with friends clients, bought out their family's "startup" and put their kids on the payroll, started their own charity that functionally does nothing, and employed people to be their personal butler assistant, and contracted out their everything to other friend's businesses, then those are considered "expenses". The actual profit has been "reinvested back into the business" and the tax is applied to what is basically pocket change because the money has been spent. It doesn't matter that the gold toilet in the CEO's personal office bathroom isn't necessary, it still counts as an expense. The core problem persists, the only thing it just changes the numbers on the documents.
"Reducing tax" is how companies strengthen social imbalance by consolidating power amongst a small group of people and exploit global markets. It's not something to write off as an understandable necessity. This is why GDPR specifically targetted revenue instead of profits as the base value.
But it's late and I may have missed a key phrase or three in the article. That also happens.