OECD officials say they have long tried to get Panama to agree to their common reporting standards on exchanging tax information, to no avail.
However Panama's Foreign Ministry announced Tuesday that the country had inked its adhesion to the Organization for Economic Cooperation and Development's reporting standards.
Foreign Minister Luis Miguel Hincapie delivered the document to OECD headquarters in Paris. The new membership however does not take practical effect until 2018.
The public gained its first access to the Panama Papers records of over 200,000 secret offshore companies when the International Consortium of Investigative Journalists (ICIJ) put a searchable database online in May.
The database, built on just a portion of the 11.5 million documents leaked from Panama's Mossack Fonseca law firm, reveals more than 360,000 names of individuals and companies behind the anonymous shell firms.
The Panama Papers reveal the full extent to which the world's wealthy, alongside criminals, create nominee companies to stash and transfer assets out of sight of the law and tax officials.
Reports already published in April based on the explosive dossier linked some of the world's most powerful leaders, including Russian President Vladimir Putin, British Prime Minister David Cameron and others to unreported offshore companies.