The FAI has said the five million euro payment from FIFA was accounted for in its financial statements for 2010.
But FAI's Chief Executive John Delaney said the payment was not specifically disclosed because of a condifentiality agreement with FIFA.
Released documents which it says give the exact timelines surrounding the pay-off following Ireland's controversial defeat in the World Cup play-off against France in November 2009.
The money was used to offset the FAI's debt over the building of the Aviva stadium.
Initially, John Delaney said the loan was compensation for the infamous Thierry Henry handball incident.
However last night, he said the FAI's potential legal case against FIFA was not just based on that goal, but also on FIFA's decision before the play-offs to seed the draw, and by the "reputational damage" caused when Sepp Blatter mocked the FAI's suggestion of being the 33rd team in the World Cup.
Meanwhile Sports Minister Paschal Donohue has said he had no knoweldge of any such deal between the FAI and FIFA.
