A third of self-assessment taxpayers do not pay as much tax as they should, meaning the Treasury is missing out on £8 billion a year, new research by the Social Market Foundation revealed.

More than three million of the ten million people who complete a tax return each year do not pay the full amount of tax, contributing to the annual tax gap of more than £30 billion revenue that goes uncollected.

The findings were revealed in a new research briefing by Dr Arun Advani of the University of Warwick and Centre for Competitive Advantage in the Global Economy (CAGE).

HMRC will release this year’s overall tax ga...