Mossack Fonseca & Co. was a Panamanian law firm and corporate service provider. It was, at one time, the world's fourth largest provider of offshore financial services. From its 1977 foundation until the April 2016 publication of the Panama Papers it remained mostly obscure, even though it sat at the heart of the global offshore industry, and acted for about 300,000 companies. More than half are registered in British tax havens â as well as in the UK. The firm received worldwide media attention in April 2016, when the International Consortium of Investigative Journalists published information about its clients' financial dealings in the Panama Papers articles, following the release of an enormous cache of its documents from between 1970 and 2015 leaked to the news media.