The cost of the extension of the Australian War Memorial is higher than the $498 million announced with much fanfare last November.
A detailed examination of the figures reveals that in previous years another $8 million dollars was spent preparing a "business case" where different options were looked at.
This figure was not bundled in with the $498 million because it occurred in a previous financial year. This means that the full cost of the expansion cannot be ascertained but it will have exceeded half a billion dollars.
A spokesman for the Memorial said: "The money was allocated to develop the detailed business case and is separate to the $498 million (over nine years) was budgeted by government."
The spokesman said the money spent on the business case actually came in under budget.
"The Memorial was initially allocated $11.4 million to develop the detailed business case, but was able to deliver it for $8.29 million, representing value for money and appropriate use of government funding."
The new figures were sent to the Senate as part of the parliamentary monitoring of War Memorial spending. Other departments and government institutions have to list items of substantial spending in the same way.
The figures also show that the War Memorial contracted consultants, O'Keefe and Partners, at a cost of $448,000 for two years to advise on fundraising, what was called "development and advancement of the integrated fundraising campaign".
The War Memorial spokesman said: "The Memorial sought to develop cohesive strategy for income generation through non-government sources, which is a common practice among cultural institutions.
"The Memorial utilised non-government funding to engage O'Keefe and Partners. This income and expense is entirely separate from the federal funding for the redevelopment program."
Despite the Memorial expecting to seek the heritage green light for the expansion needed from the federal Environment Minister Sussan Ley by June, she is yet to receive a referral.
The War Memorial is yet to apply for approvals needed from the federal agency managing Commonwealth land, the National Capital Authority.
The Memorial spokesman said it expected a submission for early works approvals would be processed "imminently".
The War Memorial on Wednesday will consult Reid and Campbell residents about plans to extend its underground car park to provide more parking spaces required for its additions.
Memorial director Brendan Nelson said the car park extension would be the first stage of early works for the institution's major expansion project.
"Currently, all early works will be within the Memorial site," he said.
The War Memorial would also build temporary on-site parking at the rear of Poppy's Cafe for builders and contractors.