Most experts believe that the current rate of 18 per cent will increase to 25 or 30 per cent, although an equalisation of income tax and CGT at 50 per cent has not been ruled out.
The discrepancy between income tax and CGT makes the latter an obvious target in the pre-budget report on 9 December, said Peter Young, director of tax at Johnston Carmichael in Edinburgh.
"CGT was increased to 18 per cent in 2008 because people were taking advantage of the 30 per cent difference between income tax and capital gains tax rates.
"With the new 50 per cent income tax rate for earners over 150,000 from April, that difference will grow to 32 per cent."
Toby Ryland, partner in accountants Blick Rothenberg, believes the move would be seen as politically acceptable. "It would not affect the average man in the street, so it can be packaged as a measure affecting only the wealthy who can afford it," he said.
"Income tax is not coming down so it seems an obvious move."
The official forecast for CGT take in the current tax year is 2.2 billion, significantly down on previous years because of the lower tax rate and the impact of the recession on the amount of gains on which tax can be charged, said Ronnie Ludwig, partner in Saffery Champness Chartered Accountants in Edinburgh.
An increase in CGT to 25 per cent would take the figure for 2009/10 to 3.08bn, while a 30 per cent CGT rate would boost this year's take by a third to 3.7bn.
Equalising income tax and CGT at 50 per cent would raise the tax take to 6.17bn, Ludwig added.
If CGT receipts returned to the level of 2008/09, noted Ryland, a further 5.2 billion would be generated by lifting CGT to 30 per cent.
But some believe a rise may not make that much impact on the treasury's income. Mike McCusker, partner at PricewaterhouseCoopers Scotland, pointed out that CGT provided just 1.7 per cent of the total tax take last year, whereas national insurance and income tax accounted for more than half.
"In the scheme of things, CGT is not that big a deal in terms of revenue earnings," McCusker said.
George Bull, head of tax at Baker Tilly, warned that any CGT changes could backfire. "Any changes introduced by the Treasury should ensure that appropriate account is taken of inflation, reward is provided for desirable business risk, inward investment is encouraged and taxpayers are not discouraged from making disposals due to adverse tax consequences."
CGT is paid at 10 per cent for those qualifying for entrepreneurs' relief on the sale of a business.