More than 80 countries signed up to a deal that could help end banking secrecy Wednesday in what the sponsors hope will be a major step in the global battle against tax evasion and fraud.
A total 51 countries signed up to the Multilateral Competent Authority Agreement under which their national tax authorities will exchange information automatically from September 2017.
And more than 30 other countries said they would sign up a year later in 2018.
Among the first round of signatories or "early adopters" were EU countries as well as previously staunch proponents of banking secrecy such as Liechtenstein and tax havens like the Cayman or Virgin Islands.
Others, such as Austria and Switzerland, the Bahamas and the United Arab Emirates, will follow in 2018.
The signings in Berlin crowned two days of talks by the Global Forum on Transparency and Exchange of Information for Tax Purposes, hosted by German Finance Minister Wolfgang Schaeuble.
The aim is for every country to be kept fully informed about the offshore holdings of its citizens.
Tax evasion is a "scourge across the world," British finance minister George Osborne told a joint news conference with his colleagues from Spain, Italy, France and Germany.
He said the signing of the deal was a "key moment" in worldwide efforts to stamp out tax evasion.
It will "reduce the places that tax evaders can hide their money," he said, while adding that the forum's work was "not finished".
French minister Michel Sapin said it was "intolerable" that taxpayers should have to feel that some people were somehow exempt and could dodge taxes.
Economist Gabriel Zucman, a specialist in fiscal fraud, has calculated that about 5.8 trillion euros ($7.4 trillion) is stashed away in tax havens, depriving authorities all over the world of around 130 billion euros in revenue each year.
- US Act against evasion -
The international movement to end banking secrecy has gained new momentum recently with the enactment in the United States of its 2010 Foreign Account Tax Compliance Act or FATCA.
The law obliges foreign banks to report to the US Internal Revenue Service (IRS) on the offshore holdings of US clients in excess of 50,000 euros.
The move prompted five European countries -- Britain, France, Germany, Italy and Spain -- to call for a generalised automatic exchange of information in 2011.
Following months of talks, amid fierce resistance in countries such as Luxembourg and Austria where banks continue to uphold banking secrecy, the EU finally came up with an accord two weeks ago.
"The more countries sign up, the more difficult it will be for others to attract investment," said the OECD's director for tax policy and administration, Pascal Saint-Amans.
However, a number of financial centres remained a "source of concern", he said.
Panama, for example, still has not set a concrete date for its exchange of information, and Singapore has not joined the process.
Saint-Amans said the OECD would compile a list of countries that do not automatically exchange information, a measure that could act as a disincentive for investment funds and international organisations looking to invest in those countries.
- Banking secrecy lives on -
But experts in fiscal fraud, such as Andres Knobel of Tax Justice Network, believe such a "blacklist" would prove a rather feeble deterrent.
FATCA puts the thumbscrews on the banks themselves, retaining 30 percent of their revenues in the United States if they do not disclose the information, he noted.
The deal signed in Berlin was therefore "an important first step (but) will not definitively bury banking secrecy," he argued.
Tax Justice Network also identified a number of potential shortcomings in the OECD deal.
In order to exchange information in 2017, the banks will collect the data from 2016 on accounts holding more than $250,000. The delay will be sufficient for tax evaders to carve up their assets and place them into multiple accounts.
Countries will also be able to decide on a case-by-case basis which information will be automatically exchanged.
Switzerland, for example, has said it will hand over information only to countries which are important for Swiss industry. Thus, the holdings of wealthy citizens from poor countries will not come under scrutiny.
Tax evaders could also hide behind "smokescreen" companies or foundations in certain cases where banks are not always obliged to reveal the identity of the account holder.