The Taoiseach has told the tribunal that he used to sign blank cheques drawn on a Fianna Fail bank account and leave them to be filled in or countersigned by Mr Charles Haughey.
In a memorandum of evidence given to the tribunal, Mr Ahern said that in dealing with the leader's allowance account, for which he was one of three signatories, he had "no recollection of ever having signed a cheque made out to cash in any significant amount".
However, he accepted that four cash cheques, totalling almost £50,000 and dating from 1989 and 1991, bore his signature.
He said he could only assume all had been pre-signed by him with the words and figures on each cheque completed by someone else.
According to counsel for the tribunal, Mr John Coughan SC, Mr Ahern said that the practice of presigning blank cheques was put in place "for administrative convenience" due to "the volume of transactions through the account combined with the necessity for the regular writing of cheques".
The Taoiseach said a series of cheques would be pre-signed by a signatory on the account and thereafter the appropriate co-signatory would sign the cheque with the details of the payee and the amount inserted.
The only signatories on the account were him, Mr Haughey and Mr Ray MacSharry who, according to the account administrator, Ms Eileen Foy, would not have signed any cheques after he became European Commissioner in 1989.
Mr Ahern said that the conduct of the account was "believed to be proper" as it was administered by "a highly competent and efficient administrator and bookkeeper".
In addition, he said, "there was no evidence of any irregularity applied to the use made of the cheques which were drawn on the account".
With respect to a £25,000 cheque made payable to cash and drawn on the account on June 16th, 1989, Mr Ahern said it was written close to the time of the general election, held on June 15th 1989.
Mr Ahern said he believed the likelihood was that he pre-signed a series of cheques in advance of the election "to allow the account to be operated so that normal business and trading debts could be discharged promptly."
He said the cheque bore his signature but the writing of the word "cash" and of the sum, both in numbers and letters, was not his.
The tribunal heard the £25,000 cheque was subsequently lodged in a Guinness & Mahon Amiens account, controlled by Mr Haughey's personal financial adviser, Mr Des Traynor.
Ms Foy said the payment could not have related to any known party function or expense.
Mr Ahern said his position was the same for the three other cheques signed by him and Mr Haughey and made payable to cash.
These were a £5,000 cheque dated April 4th, 1991, a £10,000 cheque dated September 11th, 1991, and a £7,500 cheque dated September 18th, 1991.
He said he would not have signed the cheques if the words and figures had been filled in and so they must have been pre-signed by him.
