A tax on Lloyds, Royal Bank of Scotland and Barclays
British banks might think they got off lightly.
The new bank levy announced by the Chancellor George Osborne will raise more than double the £1bn he said would be generated from such a tax when outlining his plans prior to the election - or £2.5bn a year by 2013/14.
But that £2.5bn is a fraction of what the Tories' coalition partners, the Liberal Democrats, wanted to extract from the banks.
And the tax rate - 0.04% next year, rising to 0.07 in 2012/13 - is well short of the 0.15% rate proposed by President Obama (although his tax would die after a bit more than $100bn has been raised).
Which probably explains why banks' share prices didn't move much today (Lloyds up, RBS up less, Barclays down a bit).
So the prevailing mood in the Treasury tonight will be one of slight frustration that they didn't set the rate a bit higher to raise more incredibly useful wonga, given that investors were plainly discounting something worse.
That said, the levy - which is fixed only in the generality, and will be implemented in January after a period of consultation - is an important new tax.
That 0.07% rate will apply to banks' total liabilities, minus Tier capital, insured retail deposits, repos secured on sovereign debt and policyholder liabilities of retail insurance businesses within banking groups.
If that's all gobbledegook to you, I will attempt to translate.
The charge will be levied on that part of a banks' funding that is perceived to be less reliable, viz the money provided by other banks, financial institutions and wholesale creditors. This is the finance which dried up in the summer of 2007 and started the chain of calamities known as the credit crunch - which in turn precipitated the great recession of 2008-9.
So excluded from the levy will be capital that is there to absorb losses, deposits from the likes of you and me - those oh-so-dependable retail deposits - and most financing provided by central banks. What's more there will be a lower levy rate - 0.02% rising to 0.35% - on wholesale funding where the repayment date is more than a year away.
In other words, there are two ways of looking at this levy: as a money raising exercise; and as a penalty for banks perceived to be financing themselves in risky ways with the potential to impose costs on society, on taxpayers, if it all goes wrong.
Or to put it another way, the government is signalling that it wants banks to reduce their dependence on such wholesale funding.
Which may seem like a good thing.
Except that our biggest banks have for some years provided many tens of billions of pounds of loans - especially mortgages - on the back of such wholesale finance.
So if they were to reduce their dependence on wholesale finance, there is a reasonable probability that they would cut back on the useful credit they provide to households and businesses, especially in the short term.
Which would not necessarily be such a good thing while the economy remains somewhat fragile.
That said, the levy has been calibrated at such a low rate that it would probably be wrong to expect massive behavioural changes - apart, that is, from the reduction in dependence on wholesale finance that is being independently demanded by regulators.
So which banks will pay the most?
Well no bank with eligible liabilities less than £20bn will pay a bean. Which would certainly rule out most of the building societies and smaller banks - although on the basis of its 2009 balance sheet, Nationwide would pay the levy.
But the tax would be applied to the global consolidated balance sheets of British banks, the UK subsidiaries or branch balance sheets of foreign banks, and the balance sheets of UK banks that are part of non-banking groups.
What that says to me is that Lloyds, Royal Bank of Scotland and Barclays will all pay a fair whack - because each of them are significant users of wholesale funding, and have very substantial balance sheets.
But HSBC and Standard Chartered will get off pretty lightly, because they are relatively light users of wholesale money and they finance most of their lending through customer deposits.
Which may be just as well, because HSBC and Standard Chartered are the two banks which would find it easiest to relocate their head offices to parts of the world where there's unlikely to be such a levy (in their case, Hong Kong and Singapore, respectively).
As for the related danger, that this levy on the UK operations of the likes of Deutsche Bank, BNP, Goldman and so on will persuade those banks to emigrate from the City of London - thus depriving the UK of employment and other tax revenues - that's much less likely to happen if the US presses ahead with the bank tax I mentioned above and the likes of Germany and France make good on their promise to impose similar taxes.
So long as the home countries of the biggest banks operating in the City also impose new bank taxes, the UK economy can prevent a mass exodus of banks - so long as arrangements are put in place to prevent these banks being taxed twice (which the Treasury says is part of the plan).
That, of course, only confirms my view that when the dust settles, this tax will end up being paid mainly by the troika of Lloyds, Royal Bank and Barclays - and can therefore perhaps be seen as permanent punishment for the way they held the economy to ransom in late 2008.