SSE plc — the Perth based energy company that has almost 9 million UK customers —was announced as the first FTSE 100 company to have been awarded the Fair Tax Mark today. That's a bit of a landmark for tax justice campaigners.

After more than a decade of campaigning for change with regard to tax, tax havens, corporate reporting of tax and pressure being brought to bear on governments to create change in all these issues the time had to come when things needed to change on the ground and corporate behaviour had to begin to change to match the reality of people's expectations. One company does not make a revolution, but after the announcement in September that FTSE 350 company Go Ahead Group plc had been awarded the Fair Tax Mark, SSE's joining the group of companies pioneering this Mark does represent a real step forward in corporate awareness of the importance of tax to people in this country.

SSE did not get the Mark without some effort. What the Fair Tax Mark expects from companies is reporting on tax issues that goes way beyond current Stock Exchange, company law and regulatory requirements. This is not token gesture stuff either.

So, for example, law requires that a company explain its overall corporation tax rate but as all journalists and other users of accounts know, a multitude of sins can be hidden behind that figure. What SSE is now explaining is its current tax rate, and then separately its deferred tax rate. That's important, because it's the current tax rate that reflects what will be paid to government and so is the figure most people are interested in. Mix current and deferred tax (which may be paid one day, but without saying when) together, as law currently permits, and no one has a real clue why a company is, or is not, settling its expected tax bill. For SSE this story is important: it's paying more tax than most people might expect. It's getting that on the record.

But in the area of deferred tax it's also saying something that most companies come nowhere near explaining, which is what part of its deferred tax bill might be due in the foreseeable future. This is pretty important information for investors as well as stakeholders.

And, from a tax campaigner's perspective it's notable that SSE talks about why it has used an Isle of Man company — but then also makes clear that the company in question is wholly taxed in the UK. This is accountability at a level almost unknown on such issues.

As too is the fact that SSE is reporting its results on a country-by-country reporting basis — which in its case means splitting them between the UK and Ireland in a way that it has not done before. This pioneers reporting on this basis in the FTSE 100 in a way that matches the recent demand of the OECD for the production of this type of data for tax purposes, but which the G20 did not have the courage to demand be placed on public record, where this type of accountability is essential if companies are to really be held to account for their actions.

Accountability is right at the core of this. SSE has adopted a new tax policy as a result of this process of being awarded the Fair Tax Mark, and in doing so makes clear that it will not undertake artificial tax planning and nor will it use tax havens to save tax.

In the process SSE has done three things. First it has shown that this type of reporting is possible. Many have said it is not, and having a FTSE 100 company prove otherwise is vital.

Second, it has made clear that it realises tax is important to its customers — and that their opinion matters on this issue. That shows how far tax has moved up the policy agenda. It's now making real waves and is enough to have commercial significance. There is clear indication here that in their opinion SSE thinks that tax justice pays.

And third, SSE have thrown down a gauntlet to other companies by effectively suggesting that they should follow in their path and also put their tax affairs on public record in this way.

The Fair Tax Mark was created to indicate those companies brave enough to take the step of really engaging with being transparent on tax. That's an essential part of tax justice. It's welcome to see that it's now arrived in the FTSE 100, and SSE are to be applauded on their courage in taking this step — and on the story they have to tell.

Now, who is next?