Members of the public will have four weeks to comment on the War Memorial's expansion plans after the institution was advised their national significance justified extended consultation.
The Department of Agriculture, Water and the Environment said it understands the memorial is still preparing documents for a 20-business day public comment period on the memorial's website.
The memorial said the department had advised the period was appropriate given the project's significance.
Earlier documents submitted to the Environment Department in February show one part of the planned expansion, the extension to the CEW Bean Building, will involve 5115 square metres of construction works before its scheduled reopening in 2023.
The building, constructed in 2006, would contain more administrative staff and would be integrated with a new research centre adjacent to Poppy's Cafe.
The documents submitted to the Environment Department said the CEW Bean Research Centre will "provide efficient and secure access to the national collection".
Once the period for public comment on the expansion has ended, the memorial will submit its final preliminary documents to the department, including its response to submissions made during the consultation period.
An Environment Department spokesperson said it was yet to be notified when the documents for the expansion project were likely to be submitted. There was no statutory timeframe binding the memorial, the spokesperson said.
"The department will assess this documentation and make a recommendation to the minister (or delegate) on whether or not the proposal should be approved and with what conditions, if required," the Environment Department spokesperson said.
The war memorial has received the department's approval to amend environmental documents to include the research centre, the extension to the CEW Bean Building, and changes to the parade ground, projects that were part of the original redevelopment plans.
Executive project director for the memorial development Wayne Hitches said the proposed works for the CEW Bean building and parade ground were part of the original scope and fit within the initial project schedule.
While the memorial originally intended the environmental and heritage approval to be run in two stages, it had since decided to change it to one overall submission, he said.
"There has been no change to the development project, or the public's review opportunity," Mr Hitches said.
The update to the environmental approval documents would give "a cumulative view of all development project works", he said.
Under the memorial's planned $498.7 million expansion, Anzac Hall would be demolished and rebuilt with additional gallery space. A glazed courtyard would connect the main building and Anzac Hall.