In June, the European Commission announced a formal investigation into the State's tax dealings with the computer giant.
The Brussels-based body is concerned that Ireland might be giving the company special treatment on tax that breaches EU rules.
On Monday, the Commission will publish what has been described as a lengthy, technical document setting out the parameters of the investigation.
The Government has said it will vigorously defend itself in the probe. Apple insists it has never had any special consideration from Irish officials.
It's been wall-to-wall talk of corporate tax recently. Is all this linked?
Yes and no. It's ultimately the same objective and theme, but different organisations are pursuing different elements of a bigger project - to clamp down on tax avoidance by big, profit-making multinationals.
So who's doing what, then?
Earlier in the week, the US announced it was targeting so-called corporate inversions. This is when a US corporation avoids US taxes by buying or setting up a foreign company in a country, such as Ireland, and then moving its tax domicile to that country.
Separately, the OECD is working on ways to tighten tax rules and international treaties, and to increase government tax information-sharing.
Its work is focusing on tax planning strategies by big multinational companies that exploit loopholes to make profits 'disappear' for tax purposes.
My head hurts. So what's next?
Expect the pain to set in, because there's more. The Apple probe could take some time, perhaps years. There'll be talk of tax in the Budget and expect more talk about the possible closure of the so-called Double Irish, where profits routed through Ireland end up in a tax haven.