Tribunal chairman Judge Alan Mahon yesterday granted a request for an order of discovery into the bank accounts of former chief fundraiser for Fianna Fáil, Des Richardson.
However, he restricted the order, to be sent to 71 financial institutions, to accounts held by or for the benefit of Mr Richardson between January 1992 and December 1996.
Tribunal counsel had requested access to all accounts up to November 2007.
Counsel for Mr Richardson, James O'Callaghan, had asked that the order be restricted to between January 1992 and December 1994.
Judge Mahon said that evidence suggested that some payments to Taoiseach Bertie Ahern were channelled through two bank accounts of companies associated with Mr Ahern.
He said it was "necessary and appropriate" to expand the inquiry to include bank accounts linked with Mr Richardson.
"The tribunal must remain conscious of the fact that if significant payments, and I emphasise the word if, were made by or on behalf of Owen O'Callaghan to Mr Ahern, it does not necessarily follow that such payments were not made indirectly through one or more individuals or companies and in a variety of amounts," Judge Mahon said.
"Hence the need to examine various bank accounts of a variety of individuals and com-panies in some detail."
He added that, if necessary, the tribunal would consider making other orders for periods before 1992 or after 1996.