Mark Field is a member of the Intelligence and Security Committee and MP for the Cities of London and Westminster

Well, perhaps there isn’t as much money squirreled away in Swiss bank accounts as we all thought!

In the 2012 Autumn Statement, the Office of Budget Responsibility faithfully assured us that £3.1 billion would be raised from the Treasury’s much-heralded deal with the Swiss authorities. This projected windfall not only highlighted the UK’s avowed intention to lead the way internationally by getting tough with tax evaders, but also enabled the OBR to post lower projected borrowing figures for 2012-13 than in the previous tax year.

The timely and welcome return to economic growth has made these contentions rather less important, but how exactly did the HMRC end up almost £2.5bn out of pocket? In truth, far less money held in Swiss bank accounts was found to be non-compliant than had been anticipated when the UK and Swiss authorities signed up for this deal twelve months ago.

Naturally, the conspiracy theorists, including Parliament’s own Public Accounts Committee, have eagerly claimed that this reflects only the ease and speed with which money can be – and has been – moved out of secretive Switzerland’s banking system once this initiative was announced with such a fanfare. But before we all renew a frenzy of banker-bashing, it is worth looking at a series of more mundane explanations.

What seems evident is that many people with assets in Swiss accounts have adopted the disclosure route as opposed to paying the withholding tax anticipated by the UK authorities. In time, this will generate overall revenues, but not in the way HMRC envisaged. The general spirit of the age towards openness and transparency has been a key driver here.

Secondly, the proportion of non-domiciled individuals banking in Switzerland is probably much higher than was thought when these arrangements were drawn up. Non-doms living in the UK are subject to specific tax rules.  Those rules apply no matter whether the assets are held in the UK or in Switzerland.  For this reason, non-doms are not subject to additional UK tax under this treaty. As Andrew Tyrie, the exquisitely independent=minded Chairman of the Treasury Select Committee, reported as long ago as February, the UK has massively “overstated its assumption”.

The Anglo-Swiss agreement had four main elements; a one-off levy applied to existing Swiss assets owned by UK residents (this was supposed to bring in the substantial windfall for 2013-14), a withholding tax on future income and gains (arguably to bring in around £300 million per annum), a 40 per cent inheritance levy and a duty for enhanced exchange of information.

The fact that the Swiss bilateral treaty is bringing in less revenue than HMRC envisaged does not mean that the deal should be interpreted as a failure. The deal is set to raise much more than was envisaged by its detractors.  It is also raising much more than the alternatives. While the Swiss agreement will yield around £800m for the UK Exchequer in 2013, this compares with £12m raised under the EU Savings Tax Directive in 2010.

Nor should the lower-than-expected tax yield to our own exchequer be regarded as a reflection on the lack of compliance or co-operation of the Swiss banking fraternity.  The Swiss authorities have been making major efforts to address the issue of untaxed wealth sitting in Swiss bank accounts. In fact, huge strides in adopting new transparency protocols have been made globally over the past couple of years, for which the UK government should rightly take credit. The ongoing drive to full and open exchange of information, designed to ensure that the global super rich do not evade paying tax in any of the jurisdictions in which they have financial interests, continues apace. For all the negative press headlines, this initiative has proved a genuine policy success story for the UK Treasury.