Investors in Ross Asset Management - NZ's largest ponzi scheme - have been given until the end of January to join legal action being taken against the ANZ.
A statement of claim was filed at the High Court in Wellington on July 12 with investors alleging ANZ breached its duties as banker in managing the Ross Asset Management bank accounts and for actions known as "knowing receipt" and "dishonest assistance".
Wellington financier David Ross was jailed for 10 years and 10 months in November 2013 after he defrauded more than 700 clients of $115.5 million.
Only about $10m has ever been recovered.
The ANZ has said it was also misled by David Ross - the former head of the fake investment firm.
A spokeswoman for the bank has said it denied the allegations and would be defending the claims.
In a statement released today the investors said they had now been given approval by the High Court in Wellington to take the class action claim against the ANZ as a representative action on behalf of all investors who opt in.
Investors will have until January 31, 2020 to do so although the investor group said two thirds of the eligible investors had already joined the claim.
Investor group spokesman John Strahl said: "We are very pleased to have these court orders granted so that all eligible investors have an opportunity to join the claim."
Strahl previously told the Herald there were 651 investors eligible to join the claim, although some had passed away since making the investment and he was now dealing with their estates or trustees.
Despite RAM being Wellington based, the investors were spread around the country.
"There are lots in Auckland, lots in the South Island and in obscure places like Feilding."
He said it was largely sold via word of mouth, with Ross travelling around the country talking to people.
Strahl said investors were mostly retirees, with some having multiple millions invested and others tens of thousands.
He said the group would now work hard to ensure others, who might be unaware of the action, got the chance to join it.
"It is fair to say that given the time that has passed a number will have simply washed their hands on this sorry chapter in New Zealand corporate history.
"Investors who wish to join the class action should sign up as soon as possible as only those that have signed up will be eligible for compensation if the case is successful."
The action is being supported by LPF Group, the largest New Zealand based litigation funder which specialises in funding representative actions and large commercial claims.
LPF will fund the costs of the claims on behalf of the investors and will take a fee if successful.
If the claims are unsuccessful, LPF is required to pay the costs of the claims so investors should have no need to pay anything.