Bertie Ahern told the tribunal Celia Larkin kept "a very perfect record" of all the money they spent on the house she shared with him at Beresford, Drumcondra.
This went right down to very small amounts of money, he added, and all this information had been given to the tribunal.
They had done up the house, which was being rented from businessman Michael Wall, in the summer of 1995, he said.
There were not many bills, although separate payments had to be made for an attic conversion and the changing of sanitary equipment. Mr Ahern said he gave Ms Larkin the money to pay these bills in cash, and one sum was in sterling.
Des O'Neill SC, for the tribunal, said the sterling element in the transactions under scrutiny by the inquiry amounted to £68,000.
This represented a very large volume of cash in the year in which the transactions took place, when compared with a number of factors, including Mr Ahern's salary.
Mr Ahern said he did not want to be counting in money that was not his. One of the sums, £28,000, belonged to Mr Wall. "It was never my money."
Mr O'Neill said this money went through Mr Ahern's office nonetheless. But even excluding this sum, it was still a sizeable amount of money.
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