The coming week could be a huge one for businesses in Ireland, particularly large domestic and multinational firms.

That's because negotiations around a new global corporation tax framework could be about to reach a crescendo.

Depending on how things pan out over the next few days, the result could be a dramatic shift in Ireland’s corporation tax policy.

For so long, the 12.5% rate has been Ireland’s calling card, the bedrock upon which a vibrant and lucrative export-oriented economy has been built, which in turn has become a powerful driver of economic growth.

Remind me about why change is being sought?

Pressure has been growing steadily in recent years for a substantial overhaul of how corporation tax is calculated, how much is levied and where it is paid.

Many countries were growing frustrated with big companies, particularly in the tech space.

These were firms making large amounts of money in their territories but could avoid paying much (if any) tax locally because they didn’t have actual operations there.

Governments were also becoming annoyed that aggressive tax planning was being used to shift profits around the world to lower or zero tax locations.

So where does the OECD come into it?

The annoyance of states who were losing out because of this situation began leading to some of them threatening to break away from the global tax norms and instead pursue their own policies, like placing special taxes on large digital firms, like Facebook, Google and Amazon.

Left unchecked, that had the potential of leading to a bit of free-for-all that could have resulted in a hugely disruptive, bureaucratic and disparate system across the world.

So under the auspices of the Paris-based Organisation for Economic Co-operation and Development, a process began to try to bring about a global accord on corporation tax reform.

It has been running for several years, with 139 countries taking part.

But now it looks like it is about to reach endgame.

OECD headquarters in Paris - it is aiming for a global accord on tax

And what has been proposed by the OECD?

Last November the OECD announced that 130 of those 139 countries and jurisdictions had signed up to a plan that would bring sweeping new reforms.

Under the proposals, countries would be able to tax the profits of large companies in markets where they are earned regardless of whether they have a physical presence there.

The framework also proposed that a global minimum tax rate of "at least 15%" will be set.

The rate would apply to companies with turnover above a €750 million threshold, with only the shipping industry exempted.

The sense in Government is that the negotiations have been heading in a positive direction, but nobody is yet certain that Ireland will get enough of what it wants.

The OECD said the plan will ensure that multinational enterprises pay a fair share of tax wherever they operate and would provide much needed revenue for governments, as well as stability.

Those that signed up to the plan represented 90% of global GDP, and included the US, China, the UK, France and Germany.

Since then a number of other holdouts have also signed up.

But Ireland hasn’t, right? Why is that?

No the Government wasn’t among the original 130 signatories, leaving it very much out in the cold.

Ireland doesn’t have a major issue with the first part of the plan, which would give countries a right to tax firms on the basis of business they do in a country, even if the company doesn’t have a major operation there.

The problem Ireland has is in the second part of the draft deal, which sought to set a global minimum tax rate of "at least 15%".

Ireland doesn’t want to give up its 12.5% rate at all, if it can help it. And if does have to, it wants the new rate to be as low as possible.

There is a private acceptance in Government circles that 15% would be a reasonable compromise in the circumstances.

But only if the agreement were to offer certainty and stability of a fixed 15% - not 15% or more.

It was therefore not overly surprising that Ireland didn’t sign up at the start.

Not when the absolute finish line of the negotiations had yet to be reached and there were lots of variables in play, including the question of whether the plan would even get through the US Congress.

And so, since then, Irish officials, as well as the Minister for Finance, have been negotiating hard with anyone who will listen for the "at least" part of the description to be removed.

Key to the negotiations is also what "carve-outs" or exemptions from the new global minimum rate will also be included.

So what is happening this week then?

The expectation is that the latest, possibly final, draft agreement will be circulated to all the participating countries in the coming days.

When that happens, it will quickly become apparent whether Ireland has been successful in its lobbying efforts or not.

If it has been, then the Government will have to face a difficult decision as to whether or not to relinquish the 12.5% rate – a key weapon in Ireland’s foreign direct investment armoury that has been closely guarded for decades – in the hope that by doing so now, it will limit the longer-term damage.

And if it hasn’t been successful, then the Cabinet will face an even more difficult decision of whether to stay out of the agreement, leaving it very much as an outlier in the global economy.

Or it could decide to sign up to whatever the text proposes, including perhaps the "at least 15%" clause, because staying outside the agreement is no longer tenable.

To complicate the decision-making process, it is still not clear how US tax reforms proposed by the Biden administration will pan out and whether they will complement the global plan.

The sense in Government is that the negotiations have been heading in a positive direction, but nobody is yet certain that Ireland will get enough of what it wants.

Ireland is a very small global player. But it does have many friends in the US and Europe and a thriving collection of foreign multinationals that have plenty of leverage in their home markets.

On Friday, representatives of the 139 countries involved in the process will hold a full meeting at the OECD at which it is expected that a final agreement could be inked.

It is not a complete certainty that the process is at the end and the deadline could drift.

But all the signals are that decision time is drawing near for the Government.