The former Fine Gael Senator and TD said he did not agree with Frank Dunlop's suggestion to categorise all payments to him as political donations.
Mr Dunlop has told the Tribunal that Cllr Cosgrave said to him in 1997 that they would have to be very careful. The councillor denies this conversation ever took place.
He said Mr Dunlop had commented to him that the payments were legitimate but he could not explain what prompted Mr Dunlop to say it.
Cllr Cosgrave agreed that the two men had met several times in the late 1990s and that the Tribunal would have been discussed in very general terms.
Earlier, Counsel for the tribunal, John Gallagher, repeatedly put it to Cllr Cosgrave that he ignored the advice of the county manager when he supported the re-zoning of land in 1997 at Carrickmines in Dublin.
Cllr Cosgrave said it was up to councillors to decide on the development plan, not the county manager.
He identified a report in 1990 which stressed the need for more industrial development.
However, the Tribunal heard that a council official said this advice was overturned when the council changed its policy.
Cllr Cosgrave denies he was bribed by Frank Dunlop to support a number of re-zonings.
