The offences carry maximum penalties of between 7 and 10 years imprisonment.
"The collapse of South Canterbury Finance was one the most significant of all the failed finance companies,'' Feeley said.
"The value of the fraud alleged to have been committed exceeds anything in the history of white-collar crime in New Zealand, and the time we have taken to complete this matter is a reflection of that scale,'' he said.
Feeley went on to say that it was not appropriate to comment on details of the allegations, but he said investigation itself had been "one of the most resource-intensive and time-consuming in recent history''.
The SFO said that it could not confirm the details of the allegedly fraudulent transactions, or who was alleged to have been involved in each of them.
However, the total estimated value of allegedly fraudulent transactions was about $1.7b, which included an estimated $1.58b from entering the Government's retail deposits guarantee scheme.
Feeley said the SFO had not investigated all transactions concerning South Canterbury Finance, given the number of transactions involved, but he said the office had not ruled out the possibility of investigating other matters.
The SFO has been working closely with the newly formed Financial Markets Authority (FMA) in the case. The FMA would provide support in relation to some charges.
FMA chief executive Sean Hughes said FMA was also examining avenues to take civil proceedings in order to "recuperate'' some of the money paid out to South Canterbury Finance investors under the retail deposit guarantee scheme.
The FMA would supply particulars of allegedly false statements in two South Canterbury Finance's prospectuses to support some of the 21 charges.
The statements related to the level of loan impairments and the availability of banking facilities, Hughes said.
As with other investigations into failed finance companies, the FMA had worked closely with the SFO on the case.
"A single prosecution is more efficient and is consistent with FMA's enforcement policy, which allows for joint prosecutions where appropriate,'' he said.
"We have also taken into account the fact that the Crimes Act charges laid by the Serious Fraud Office carry heavier maximum sentences than Securities Act charges targeting the same behaviour,'' he said.
South Canterbury Finance founder Allan Hubbard died in a car crash in September, ending an 18-month long chain of events that began with the government putting Hubbard, his wife Jean, and some of business interests, under statutory management.