13 Oct 2025HMRC brought in an extra £4.6 billion in tax revenue last year by using its 'big data' system. The tax authority's Connect system uses data from a wide range of financial sources to analyse tax returns and detect potential evasion. In a response to a freedom of information request from law firm Pinsent Masons, HMRC said it generated on average £3.4 billion in additional annual yield from Connect cases. However, this rose by over a third in the 2024/25 tax year when Connect generated approximately £4.6 billion. Connect, which was introduced in 2010, has grown in scale over the last 15 years to become one of the largest datasets held by the UK government. It has become a key part of tax investigations, with around 4,300 HMRC staff now using it. The increasing scale of the Connect system allowed HMRC to conduct more than half a million cases in the last year alone. Ian Robotham, a tax expert at Pinsent Masons, said: 'HMRC has spent time building up the amount of data sources that it can access and analyse. 'The algorithms that it uses allows HMRC to spot anomalies that would otherwise go unnoticed by the human eye. 'With thousands of HMRC staff now using Connect, taxpayers are facing a level of oversight that would have been unthinkable just a few years ago.'