The amount of tax which the government suspects big businesses have underpaid has risen to £24.8bn, up 13 per cent on last year's figures.
Analysis by law firm Pinsent Masons of the figures from Her Majesty's Revenue and Customs (HMRC), the department responsible for collecting taxes, showed this was a 31 per cent jump on the 2014-2015 tax year.
The news comes as HMRC has been placed under increasing pressure from the Treasury to deliver a bigger tax take, by increasing compliance and cracking down on avoidance.
“Another £3bn rise in the tax HMRC is querying shows that HMRC is broadening its horizons and putting a far wider range of transactions under scrutiny,” said Heather Self, partner at Pinsent Masons.
“We are seeing an increasing number of challenges to arrangements that would previously have been regarded as routine and perfectly acceptable.”
Chancellor Philip Hammond announced in November that the government would aim to raise an extra £2bn by 2022 by targeting tax avoidance.
This was widely seen as a more politically palatable way of raising cash than either cutting public expenditure or squeezing the average taxpayer for more money.
“However, HMRC is putting the affairs of more and more companies under the microscope as a result, increasing the costs for those businesses,” said Self.
“At the same time many of the largest businesses are struggling with HMRC's customer relationship manager system and finding it more difficult to get uncertainties resolved in real time.”
Pinsent Masons noted that the £24.8bn figure is the maximum potential tax liability across all enquiries under consideration. After full investigation of all cases, the amount actually due tends to be around half the initial estimate.