Half of Northern Ireland self-assessment taxpayers do not pay enough tax, according to new research.
The Centre for Competitive Advantage in the Global Economy (CAGE) study said that across the UK, over three million of the 10 million people who complete a tax return each year do not pay the full amount of tax.
The total value of tax underpaid via self-assessment is around £8bn, the report said.
Self assessment tax returns are used by those who are self-employed, run their own business or work on a freelance basis.
The research found that men are more likely to under-report than women, and by larger amounts.