Described by the former British cabinet minister Vince Cable as "sunny places for shady people", tax havens are much maligned.
It's thought the total sum hidden away in low-tax, low-regulation jurisdictions around the world could be $21tn (£13.5tn) - as much as the total annual economic output of the United States and Japan combined.
Barack Obama and other world leaders have vowed to crack down on tax havens. The Organisation for Economic Cooperation and Development (OECD) has pressed for greater transparency about how they operate. The European Commission has called for greater information-sharing about tax deals by EU national governments.
Four experts talk to the BBC World Service Inquiry programme about why, despite this growing opposition, tax havens continue to prosper.
Anthony Travers: No pot of gold sitting offshore
British-born lawyer Anthony Travers moved to the Cayman Islands 40 years ago, and is now chairman of the Cayman Islands Stock Exchange.
"The expression 'tax haven' in relation to the Cayman Islands is hopelessly outmoded.
"The reason why corporations go to the Cayman Islands is not necessarily to avoid tax. [They] will pay taxes in the jurisdictions in which taxes are due to be paid. Corporations, particularly hedge funds, that trade out of the Cayman Islands domicile there for various other reasons relating to quality of the legislation, stability, absence of intrusive regulation.
"This delusion that there's some pot of offshore gold sitting in the Cayman Islands needs to be dealt with comprehensively.
"There is no pot of gold sitting offshore. Monies in Cayman Island hedge funds or private equity vehicles are invested and reinvested and they're certainly not sitting in the Cayman Islands in any way, shape or form.
"Since all this legislation providing transparency was introduced over a decade ago, what we haven't actually seen from the Cayman Islands is any instances of major frauds or tax evasion."
Richard Murphy: Tax havens obscure activity
Accountant Richard Murphy founded the Tax Justice Network to campaign against tax havens.
"Tax havens are now serving a different purpose from tax abuse. The tax abuse is to some degree, in some of them certainly, virtually history, and it certainly isn't why large companies are now using them.
"Regulation is still stacking up in favour of large companies hiding away from view in these places, so they can get away, commercially, with lower costs than they could otherwise achieve.
"Let's be clear about what tax havens or secrecy jurisdictions mean when they say they have complied with regulation. The regulation that takes place in a tax haven is different from the regulation that might, for example, take place in the UK or Germany.
"In countries like the UK, if we say something is regulated, it takes place here and is regulated here. The characteristic of a tax haven is the transactions that are recorded there take place elsewhere. That means that whilst the tax havens are very good at regulating what takes place within them, the truth is that almost nothing takes place within them.
"Suppose we have a company that is registered in the Cayman Islands, but which trades in the UK. If the UK wanted to ask a question about that company, first of all it has to find a good reason why it needs the information, and secondly the Cayman Islands have to have a good reason to link that company to the UK.
"But if you're trying to actually open up the fact that there is a trade recorded in Cayman but happening [in the UK], you've got to be able to identify both ends, but the whole structure of it is designed not to. And also Cayman, when it undertakes its regulation, only asks about what happens in Cayman.
"Successive governments have believed it worthwhile for the City of London - and, bluntly, Wall Street - to have the advantage of having part of their activity beyond regulation, so that they could compete in ways which are considered to be innovative and which make money for the world financial markets beyond the regulatory environment.
"It is down to politicians to decide: is that a risk still worth taking? They've got to take on the vested interests in their own jurisdictions, the large companies and so on who still use tax havens."
Margaret Hodge: Companies fear reputational damage
British opposition MP Margaret Hodge chaired the powerful Public Accounts Committee for five years and highlighted legal tax avoidance. She clashed with many companies including Amazon, Starbucks and Google, whom she accused of using "smoke and mirrors" to avoid paying tax.
"What really amazed me was the resonance this whole agenda has with people wherever they are, whatever their age, whatever their gender, whatever their race, whatever their socio-economic class.
"Everybody thinks it's not fair that they should be paying tax, whilst if you're a very rich individual or if you're a big global international company you get away with finding devices which allow you to aggressively avoid the legitimate payment of taxation. It really has hit a very, very raw nerve."
It emerged that the US company Google was minimising its tax in Britain and other countries by recording most of its foreign sales - and thereby earning almost all its foreign income - in Ireland, then legally channelling it, via the Netherlands, to Bermuda, where very little tax is paid. That was possible, not just because of Bermuda's tax regime but also because of Irish and Dutch regulations which allow profits to leave their shores.
"It's Holland, it's Switzerland, it's increasingly Britain, it's Luxembourg, all these countries believe by offering low tax or the possibility of tax avoidance for global companies, they'll attract more business in.
"My point on that is that they're not really attracting business. People are shifting profits without really bringing businesses in, and therefore the world loses the tax revenue and the only people who gain are the private businesses.
"One of the interesting things that I am told has happened since we started raising these issues and the whole issue went viral, is that tax has become an issue that is discussed at board level, not just as a nuisance, you know, 'how can we minimise the tax we pay?', but as a reputational issue.
"I think the damage that's been done to Starbucks, to Google, to Amazon frightens lots of the directors sitting in board rooms today."
Jamie Whyte: Tax havens 'keep other governments honest'
Former philosopher and management consultant Jamie Whyte led New Zealand's free market political party ACT, which failed to gain any seats at the 2014 general election.
"I am a fan of tax havens, because they keep other governments honest. It's a matter of competition. A tax haven basically exploits the fact that many people in other countries want to pay less tax. And if that weren't possible, and if there were no tax havens, there would be far less constraint on how much mainstream governments could tax their population.
"I'm not suggesting it's democratic. But I think it's a very healthy constraint on some of the uglier aspects of democracy. If you found yourself, a Christian, facing a mob in a Middle Eastern country, and you found that you could hide in a church, and for some reason the population still respected the sanctity of the church, and so it was a haven for you, I think you'd be very glad of that church.
"Of course it's not democratic: the mob far outnumbers you. But until quite recently, no theorists of democracy ever believed that it should be untrammelled, that simply because a majority of people want your money they have a right to it. So I celebrate the anti-democratic aspects of tax havens.
"The US has put a lot of pressure on Switzerland recently, They can say: 'If Swiss banks don't give information to the US government about the accounts of Americans with these banks, they will cancel their banking licence in the US'. That's a way of applying an enormous cost to the tax haven.
"That works in the case of Switzerland. It might be much harder to do in the case of Malta or Gibraltar, because that may not cost them that much. I suspect that they'll never be able to eliminate all tax havens. If you drive several countries out of the tax haven business, you make the rewards to the countries that stay in the tax haven business even greater.
"[And the reputational damage argument] really only affects retail companies, Starbucks, Google and the like. They're a fraction of the companies in the world. There are many, many companies - consulting firms, law firms, you name it - who in that sense are under the radar. Nobody in the public has any idea what their tax affairs are."
The Inquiry is broadcast on the BBC World Service on Tuesdays at 12:05 GMT/13:05 BST. Listen online or download the podcast.