The Earthquake Commission (EQC) has discovered it has almost 1000 more open earthquake claims in Christchurch than it thought.
The discovery brings the total number of open claims to 3500, seven years after the earthquakes.
The commission said it discovered the oversight when it upgraded its systems and began attaching case managers to those with claims.
Chief executive Sid Miller said the oversight did not mean claimants had been forgotten.
Eighty percent of the previously undisclosed claims had had some action taken on them in the past year, he said.
The commission has already ordered an independent review of the way it collects data.
EQC minister Megan Woods has talked about the need for change in the way the commission handles claims.