The figure is now thought likely to come in around £43 billion, rather than the £49.9 billion forecast in November, delivering a knock-on boost to subsequent years.
Hammond will use today's Spring Statement to announce a call for evidence on such a tax.
There was further good news when Hammond revised down national debt forecasts to reach a relatively healthy 0.9 per cent of GDP in 2022, down from 1.8 per cent in 2018.
Mr Hammond rejected Labour "doom and gloom" over the state of the economy, saying the recession repeatedly forecast by shadow chancellor John McDonnell since 2010 had failed to materialise.
The chancellor said the economy was on track to grow a little faster than expected this year, despite the prospects for weaker growth in the medium term.
Mr Hammond said he hoped this weekend's forthcoming summit of the G20 developed nations in Argentina would help to set out some concrete steps for achieving that.
Promised to be a short update on forecasts, Philip Hammond's Spring Statement turned out to be 26 short minutes of politics: uplifting vision for the backbenchers and the television news, coupled with witty digs at the Opposition.
He will launch a number of consultations to report in time for the autumn Budget, including on the impact of VAT on small businesses and the use of the tax system to cut plastic waste.
Mr Hammond said the tech sector employed more than 1.5 million people and accounted for £6.8bn of investment in 2016, 50% higher than any other European country.
He said "substantial progress" has been made in Brexit talks. However, its forecast for coming years remained unchanged, with GDP growth expected to sit at around 1.3% until 2020.
The OBR expects inflation to fall from its peak of 3% to the Bank of England's 2% over the next 12 months.
The Office for Budget Responsiblity has upgraded its forecasts for United Kingdom growth to 1.5% for 2018, slightly above the 1.4% it predicted in November.
But all eyes will be on the Office for Budget Responsibility's forecasts for the deficit, debt, GDP and productivity, to see whether they back up the Chancellor's claim that there is now "light at the end of the tunnel".
By 2021 the growth forecast was 1.4 percent, compared with a previous forecast of 1.5 percent.
Mr Hammond said his deputy Elizabeth Truss would publish the departmental allocation of more than £1.5 billion of Brexit preparation funding for 2018-19.
Although there were no announcements on any major new policies, Hammond said that the government was on track to meet its building targets for new homes.