The Centre for Economics and Business Research (CEBR) suggests in an analysis of the scale of subsidy between different regions/countries in the UK that Scotland receives no net subsidy. The table showing estimated receipts and expenditures is here
CEBR provide no indication of the sources of their data, or their method of estimation. However, their estimate for Scotland appears to be close to the Government Expenditure and Revenues for Scotland (GERS) figures for the net fiscal balance when Scotland is given a geographical share of oil revenues. The table below shows it was -10.6% in 2009-10.
Since the UK had a deficit in 2009-10 of 11.1% of GDP the conclusion drawn by CEBR appears, on the face of it, to be correct.
But wait. If independent, Scotland would have to pay interest payments on its debt at a rate which will almost certainly be above the yield on UK Treasury's, see my posts here and here. The GERS publication shows Scotland bearing interest payments on its population share of UK debt of £2.635 billion. This relates to UK debt payments at an average interest rate of 3%, given earlier more costly borrowing than the current 2% yield and the different maturities comprising the debt portfolio. If we make the assumption that Scotland would have to pay a yield on its borrowings that average 4%, then the Scottish government outlays would rise by about £1 billion - specifically £931 million. If the yield had to be 5%, outlays would rise by £1.8 billion. If 6%, unlikely, then the additional expenditure would amount to £2.7 billion.
So, even a modest premium above UK Treasuries, equivalent to the current yield on New Zealand 10 year bonds, would cost approximately an extra £1billion a year compared with present estimated Scottish government spending in GERS.
Bang goes that £1 billion surplus of oil revenues that Alex Salmond believes he could put each year into an oil fund!