But others accuse the Paris-based economics body of drawing up a "meaningless" blacklist of one.
Trinidad & Tobago is the last remaining tax haven in the world, according to Organisation for Economic Co-operation and Development (OECD).
The Paris-based body said the caribbean state is the sole "non-compliant" tax jurisdiction of a list of 15 regions it has complied, a statement many will view as controversial.
The OECD said: "Trinidad and Tobago has been identified as the only jurisdiction which has not yet made sufficient progress towards satisfactory implementation of the tax transparency standards. Discussions are continuing with Trinidad and Tobago, and progress is anticipated soon."
The international body, which covers 142 member states, said it has made "massive progress" with the other regions on the list to bring their tax affairs in line with international standards.
The OECD said it had got other states on the list to agree to cut back on banking secrecy, improve access to accounting records and apply tougher financial enforcement.
It said that compared to last year, 13 jurisdictions have now become "largely compliant".
They are: Andorra, Antigua and Barbuda, Costa Rica, Dominica, the Dominican Republic, Guatemala, the Federated States of Micronesia, Lebanon, Nauru, Panama, Samoa, the United Arab Emirates and Vanuatu.
While it calls the Marshall Islands "partially compliant".
The drive to prise open tax havens since the financial crisis was boosted last year with the release of the Panama Papers. These leaked documents from a Panamanian law firm showed the widespread use of anonymous offshore shell companies and caused an international outcry.
The G20 nations asked the OECD last summer to draw up a list of tax havens ahead of this month's G20 leaders' summit.
But lobby group Tax Justice Network condemned the OECD list as a "meaningless gesture".
The London-based tax body said the standard the OECD was holding these 15 regions to has already been superseded by automatic tax information shared between nations.
The Tax Justice Network added that this new standard showed that "many of the usual suspects such as Switzerland, including many OECD members, are simply not going to extend transparency further than they absolutely have to".
The US has refused to share its tax information with all but a few nations, while demanding it of many others, said the Tax Justice Network.
Alex Cobham, chief executive of the Tax Justice Network, said: "If you were going to produce a tax haven blacklist with only one member, it wouldn't be a small Caribbean island – it would be tax haven USA."
Trinidad and Tobago could not provide a comment when contacted by IBTimesUK.