"This extension takes into account the number and timing of interviews of key witnesses, a prior commitment of a member of the inquiry, and the need to ensure due process is followed," Ms Bennett said.
The extension would be accommodated within the initial budget for the inquiry.
Phillip John Smith allegedly fled to South America while on temporary release from Spring Hill Corrections Facility in South Auckland on November 6 last year.
He had been serving a life sentence for the 1995 stabbing murder of the father of a boy he had sexually abused.
At the time of the murder, Smith was out on bail for the sexual offending and charges of blackmail against a man who later killed himself.
He was caught in Rio de Janeiro on November 13, a week after he left New Zealand.