If a parent offers to pay a large sum of money(around 20k) directly to the bank off their childs mortgage is this seen as a gift by revenue even though the child will never directly see any of the money?
Yes, it would be a gift, but as it's well under the threshold for CAT, there would be no immediate tax implications. It will count towards the thresholds, so if future gifts or inheritances exceed the threshold, tax will be payable.