Image copyright Reuters Leading financial institutions have welcomed a new crackdown on international tax dodging agreed by Europe's biggest five economies.
Tax and law enforcement agencies in the UK, Germany, France, Italy and Spain have agreed to share data.
The International Monetary Fund's chief Christine Lagarde said it added to the momentum building against those who sought to hide income and assets.
UK Chancellor George Osborne said it would "lift the veil of secrecy".
The move comes in the aftermath of the Panama Papers leak, which revealed how the rich and powerful hide assets, sparking widespread condemnation that the authorities had failed to act.
Under the new deal, the five nations will exchange information regarding beneficial ownership registers, which show who really owns assets.
They will also create new registers of financial trusts.
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Ms Lagarde said: "The IMF very strongly welcomes and supports this new momentum to fight corruption and tax evasion. We need to think outside the box and to that end, we at the IMF will question whether the technical assistance that we provide to anti-money laundering and to counter-terrorism financing can be better leveraged to identify what more is needed in terms of implementation."
The five countries will now push for the rest of the G20 nations to follow suit. That would mean sharing data on previously secret tax information between countries such as America, Saudi Arabia and China.
The UK government has already announced that it will make its register of beneficial ownership public - and is privately urging the other four signatories of the deal to agree that the public can have access to the information, according to the BBC's economics editor Kamal Ahmed.
Mr Osborne said at the annual International Monetary Fund spring meeting in Washington: "Today we deal another hammer blow against those who hide their illegal tax evasion in the dark corners of the financial system."
"Britain will work with our major European partners to find out who really owns the secretive shell companies and trusts that have been used as conduits for evading tax, laundering money and benefitting from corruption."
Meg Hillier, who chairs the UK's Commons Public Accounts Committee, told the BBC: "It's a good first step. One hammer blow doesn't crack a nut but it's a great start."
The agreement was announced at joint press conference of the finance ministers of the five countries at the IMF.
Mr Osborne was joined by other finance ministers, including Germany's Wolfgang Schaeuble and France's Michel Sapin.
"The current events show that identifying the ultimate beneficial owner behind corporate structures is key to fighting tax evasion, money laundering and illicit finance effectively," Mr Schaeuble said.
The OECD group of leading economies has vowed to set new global tax rules on information sharing and transparency, and promised to put pressure on Panama to adopt international standards of reporting.
The OECD's head, Jose Angel Gurria, said it was important to confront the financial experts that collude with the rich to evade tax. "We have to crank down on the professional enablers - lawyers, accountants, financial institutions and the like who play a key role in maintaining the veil of secrecy.
"This also means to ensure the loopholes which allow them to hide the beneficial ownership of companies, trusts and other arrangements. We have to make sure that those are closed."
Panama papers
It comes almost two weeks after the leak of 11.5 million documents which revealed how businesses, politicians, and criminals used secretive companies to hide tax.
The fall-out from the so-called Panama papers forced Iceland's prime minster to step aside.
And earlier Spain's acting industry minister Jose Manuel Soria said he was resigning after alleged links to offshore companies in Panama and Jersey were disclosed.
Mr Soria denied wrong-doing, but said he was stepping down to limit any damage to the government.