While the council first said additional information it required to process the application would be supplied by the end of last month, last week, the council said the Dunedin City Council had now advised it it expected to submit the additional information by the end of May.
The city council applied for consent to operate a new six million cubic metre landfill at Smooth Hill, south of Dunedin, in August last year.
But the application has been on hold since the regional council requested further information from the city council, including the criteria used for the assessment of alternative locations included in its application.
The city council last month would not say if it knew about plans for a Southland landfill near Winton to take on more waste from across the lower South Island when it applied for its own new one.
The project has proved controversial with some Brighton residents.
Last month, Saddle Hill Community Board chairman Scott Weatherall said any further delays to the application should put an end to the project.
A city council spokesman did not say what caused the additional delay, but said the time taken to complete this stage of the process reflected the size and complexity of the application.
The city council has allocated $56million in its 10-year plan to develop a new landfill at Smooth Hill.
