The October 2013 IMF report: Fiscal Monitor : Taxing Times,
Further details on the topic from page 23, in the chapter called:
The sharp deterioration of the public finances in many countries has revived interest in a capital levy, a one-off tax on private wealth, as an exceptional measure to restore debt sustainability. (1) The appeal is that such a tax, if it is implemented before avoidance is possible, and there is a belief that it will never be repeated, does not distort behavior (and may be seen by some as fair).
There have been illustrious supporters, including Pigou, Ricardo, Schumpeter, and, until he changed his mind, Keynes. The conditions for success are strong, but also need to be weighed against the risks of the alternatives, which include repudiating public debt or inflating it away (these, in turn, are a particular form of wealth tax on bondholders that also falls on non-residents).
There is a surprisingly large amount of experience to draw on, as such levies were widely adopted in Europe after World War I and in Germany and Japan after World War II. Reviewed in Eichengreen (1990), this experience suggests that more notable than any loss of credibility was a simple failure to achieve debt reduction, largely because the delay in introduction gave space for extensive avoidance and capital flight, in turn spurring inflation.
The tax rates needed to bring down public debt to pre-crisis levels, moreover, are sizable: reducing debt ratios to end-2007 levels would require (for a sample of 15 euro area countries) a tax rate of about 10 percent on households with positive net wealth . (2)
(1) As for instance in Bach (2012). (2) IMF staff calculation using the Eurosystems Household Finance and Consumption Survey (Household Finance and Consumption Network, 2013); unweighted average.
It should probably be obvious that there is one key sentence here, one which explains why the IMF is seriously considering the capital levy (supertax) option, even if it’s presented as hypothetical:
The appeal is that such a tax, if it is implemented before avoidance is possible, and there is a belief that it will never be repeated, does not distort behavior (and may be seen by some as fair). !?