EU
"Europe," she said, "is being very robust in demanding transparency, on where profits are earned and where money is made."
Of course, the UK is due to exit that club at some point in the future.
The crux of Amazon's low corporation tax bill in the UK (along with a few other multinationals) is that they can supply goods and services in the UK but say they are sold out of Ireland or Luxembourg and invoice from one of those jurisdictions, which offer them favourable tax rates - and single market rules allow them to do this. Once the UK is no longer part of the single market, that loophole would not be so attractive.