The $25 million spent on planning a new flag is only the beginning - hundreds of thousands more will be needed if a new ensign is adopted.
Figures compiled by the Ministry of Justice reveal Government departments alone will have to spend more than $660,000 to get new flags. The New Zealand Defence Force has the most flags. Its 600 standard outdoor flags will cost $459 each to replace.
The Ministry of Foreign Affairs has 318 and the Police have 157 flying at stations around the country.
The cost to replace Government department stocks of 1,278 outdoor ones, 249 indoor ones, 11 ceremonial flags and 547 that flap around on car pennants and tables is estimated at $663,612.
The figure does not take into account the 2600 schools that would need to replace the national flag.
Also not included is the cost for local councils, airports, ports, tertiary providers and state owned enterprises such as NZ Post, KiwiRail, Air New Zealand and NZTA, which issues licences that have the New Zealand flag on them.
School principals will have to decide whether they want to buy the new flag. If they do it will come out of their operational costs.
Katrina Casey from the Ministry of Education said not all schools fly the flag. "It would be up to schools to decide what they wanted to do and whether they wanted to buy a new flag out of their operational grants."
The NZTA said there would be minimal cost to the three million driver's licences with the current flag. They would be replaced as old stock ran out. "All existing driver licences would remain valid until their date of expiry," said Andrew Knackstead from NZTA.
Auckland Council flies the flag outside its civic buildings, as well as at events including Anzac Day and citizenship ceremonies. Council spokeswoman Marguerite Delbet said it would not make a decision on costs until after the referendum.
On Tuesday, the Flag Consideration Panel released the shortlist of four potential flag replacements.
A postal referendum will now take place from November 20 to December 11. The highest-rating flag will be pitted against the current flag in a second referendum next March.