The Abbott government didn't get costings from Treasury on how much revenue its multinational tax avoidance budget measure would bring.

The revelation explains why costings were not given by Treasurer Joe Hockey when he announced the measure or included budget papers.

Finance minister Mathias Cormann says there were never any revenue costings carried out on the May budget measure to tax multinationals. Credit:Alex Ellinghausen

Speaking at a Senate estimates hearing on Tuesday, finance minister Mathias Cormann said the government could not "credibly do that".

"You can only do that if you've got realistic information to be able to base such a costing on," he said, in response to a question from Labor's Sam Dastyari.