Apparently, this all hinged on whether "favourable rates" were given to Apple in Ireland.

The European Commission accused Ireland of giving Apple illegal tax advantages eight years ago but the Irish government has consistently argued against the need for the tax to be paid.

The ECJ said its decision on the matter was final and that "Ireland granted Apple unlawful aid which Ireland is required to recover".

The Irish government said it would respect the ruling, while Apple said it was disappointed with the decision and accused the European Commission of "trying to retroactively change the rules".

[bbc.co.uk...]