A total of 5,759,006 people filed online by the 31 January deadline - an increase of over 50% on the 2008 total, when 3.8m people filed online.
Welcoming the figures, Financial Secretary to the Treasury, Stephen Timms, said: "I am delighted that more and more people are recognising the benefits of filing their tax return online. Online returns make it easier and quicker to calculate how much tax you owe and you can pay online too."
Sixty seven per cent of all self assessment tax returns were filed online this year. This surge in the use of the online channel is changing the way in which HMRC provides its customer services.
Dave Hartnett, Permanent Secretary for Tax at HMRC said "HMRC's SA online and other Internet services enable people to do business with government in the way we know they want to. The outstanding popularity of online filing demonstrated by today's figures is the foundation on which we are transforming the way taxpayers interact with us."
