Mr Charles Haughey has refused to allow the tribunal to investigate a £400,000 loan taken out in 1982 at a bank in the Cayman Islands.
Counsel for the tribunal, Mr Jerry Healy SC, said the former Taoiseach had furnished waivers to allow it investigate other banks but none has been provided for Guinness & Mahon Cayman Trust, now trading as Ansbacher Cayman.
Documents from the Central Bank show Mr Haughey made an application on December 8th 1982 for exchange control permission to borrow the sterling equivalent of £400,000 from the offshore bank.
The purpose of the loan was stated as primarily for the conversion, development and extension of Abbeville Stud.
The loan was due to be repaid in full by January 31st, 1985. However, it was rescheduled, with two additional applications to the Central Bank, until January 1987.
Mr Healy said that as there were no further applications for extensions, it seemed reasonable to assume the loan was paid off. However, there was no indication as to how this was done.
In the course of his opening statement, outlining the latest phase of the inquiry into Mr Haughey's finances, Mr Healy also provided details of two current accounts belonging to the former Taoiseach into which £1,456,875.41 was lodged between January 1979 and June 1987.
An additional loan account, taken out in the name of Mr Haughey and another person, later named as the late Mr Harry Boland, had £229,756.82 credited to it between November 1981 and September 1984.
Some £74,996.83 was credited to a second loan account in Mr Haughey's name in the period September-October 1981.
Mr Healy said these sums were "very significant" and could be judged against the annual salary of £9,590 for a TD and £16,930 for a Taoiseach in 1979. The respective salaries rose to £19,295 and £32,790 by 1987.
However, Mr Healy noted "it would appear that Mr Haughey did not lodge the proceeds of his salary cheques to any of his bank accounts".