Treasurer Joe Hockey is confident Arthur Sinodinos will return to the front bench as assistant treasurer after standing aside while a corruption inquiry is underway.

Senator Sinodinos stood aside from the ministry in March pending the outcome of a NSW Independent Commission Against Corruption inquiry.

He has since appeared as a witness at the hearing, but has denied any wrongdoing in relation to his role in a water company that funnelled donations to the NSW Liberal Party.

Mr Hockey said Finance Minister Mathias Cormann had been doing an "outstanding job" filling in as assistant treasurer in Senator Sinodinos' absence, including during the budget process.

When asked if he was confident Mr Sinodinos would return to the frontbench, Mr Hockey replied: "Yep, absolutely".

"We look forward to Arthur coming back," he told Sky News on Sunday.

AAP