Mr Dermot Desmond gave Mr Charles Haughey £100,000 sterling in September 1994 after the former Taoiseach said he was considering becoming a non-executive director of an unnamed German bank, the tribunal heard.
He made a further payment of £25,000 sterling to Mr Haughey in October 1996.
Mr Desmond reiterated his claim that he had never made payments to Mr Haughey during Mr Haughey's political career (he retired from politics in November 1992).
Mr Desmond was spending his first day in the witness box and responding to questions from counsel for the tribunal, Mr John Coughlan SC, who referred him to two statements he issued in January 1998 after allegations appeared in Magill magazine.
In the statements, Mr Desmond said any payments to Mr Haughey after he retired from politics were a "private matter". Mr Desmond also told the tribunal yesterday he was not aware who the ultimate beneficiary was of an investment account in the name of Overseas Nominees, which was held with his stockbroking firm, NCB.
Mr Coughlan said Overseas Nominees was connected to Ansbacher Cayman, but Mr Desmond said he was not aware of this. He said the account was opened on the instructions of Mr Des Traynor in July 1988. Mr Desmond said Mr Traynor was the only person he ever talked to about the account.
Mr Coughlan asked where the funds came from to open the account. He said the opening balance was £105,566 and this "seems" to have come from an NCB sterling account held with Bank of Ireland. Mr Desmond said he did not know if this was the case.
When asked was he involved in particular withdrawals from the account, Mr Desmond said: "the only involvement that I could possibly have was Mr Traynor requesting to contact me and asking me to get a draft or make a payment and I would pass the instructions on to John Keilthy". Mr Keilthy was in the private client division of NCB Stockbrokers at the time.
Mr Coughlan revealed that after a withdrawal of £95,000 in March 15th, 1991, an overdraft of £23,461 was created on the account. Mr Coughlan pointed out that in previous evidence Mr Keilthy said it was "unusual" to have a client account overdrawn.
Mr Desmond responded: "I don't know the particular circumstances, because . . . if we had sold stock and there was a credit coming into this account, I would have expected that an account person would have said, `it's all right, there is money on the way' ".
He added: "Again, I am sure that it wasn't an overdraft being afforded to this client, because we decided that they were good for it, I think there must have been some other circumstances".
Mr Coughlan read out a letter dated March 19th, 1991, from Mr Traynor to Mr Desmond, the first paragraph of which read: "Many thanks for yours of March 15, together with sterling for £85,640". On the top of the letter was the reference code JKL 918.
Mr Coughlan said the letter seemed to be referring to two separate items. He said the letter could be read "as thanking somebody for facilitating the overdrawing of the account, could it not?" Mr Desmond said, "I wouldn't have thought so".
Counsel for Mr Desmond, Mr Bill Shipsey SC, said Mr Desmond would re-enter the witness box today.