The details of two further charges were amended as agreed by the SFO and Tonkin.
While the particulars changed the charges remained in place.
Tonkin pleaded guilty through his lawyer Elizabeth Bulger to one charge of false accounting; two of making false statements to cause losses or induce new investors, and one count of forging a fake audit letter.
Following today's hearing Tonkin was remanded on bail until his sentencing later this year.
Judge Couch said the Summary of Facts was "quite lengthy" and the case was complex so sentencing was likely to take "a considerable amount of time".
He set aside a half day as the "time required is extensive" for the sentencing, which would involve a significant number of victims.
The SFO said there was "in a range of 170" victims.
It was unlikley every victim would want to be heard at sentencing.
The victims cannot be identified due to a suppression order that may be made permanent at sentencing.
The Summary of Facts is still being finalised between the SFO and defence as Tonkin disputed several points in the current version.
According to the charging documents, the SFO claims that investors in Tonkin's Penrich Global Macro Fund were told the scheme was worth $137.2m in February last year, but actually had a value of only $20.7m.
The alleged fraud is believed to be one of the biggest of its type in New Zealand history.
Several family members supported him at the brief appearance.
In May the Herald revealed that Penrich collapsed suddenly in March 2020 and liquidators were appointed to its branches in London, the Cayman Islands and Christchurch.
They told investors that a "significant discrepancy" had been uncovered.
The SFO began investigating soon after.
Tonkin was later charged.
The Herald then reported that the false accounting charges relate to Tonkin's alleged inclusion of false asset values and hidden cells in the fund's "Monthly Value" spreadsheets for nearly a decade, from September 2012 until the fund's sudden freezing in February 2020.
For instance, in September 2012 the fund reported a value of $13.6m, but this was alleged by the SFO to have been inflated by $10.6m.
In 2016, a UK pension scheme noted in its annual report that it had withdrawn from the fund "due to the delay in the provision of audited accounts ... and the auditor's inability to verify the valuation of the underlying assets".
Charging sheets allege that a number of international clients stopped receiving monthly investors statements around this time, suggesting they withdrew their investments.
According to charging documents, on December 18, 2017, Tonkin is alleged to have manufactured financial statements that gave a false picture of the fund's position in 2016.
"The defendant falsely stated the total assets, total liabilities and the net assets of the Penrich Global Macro Fund," the SFO alleges in its charge of forgery.
"The defendant forged a BDO Cayman Islands auditors report and attached it to the Financial Statements."
The charges of false statements relate to Tonkin's representations to investors, both in including the allegedly fraudulent inflated value in their monthly account balances, as well as in monthly updates on his trading activity which the SFO allege far understated the level of risk and losses he was incurring.
Tonkin grew up in Christchurch and graduated from Canterbury University with an honours degree in economics, before working at Treasury, then Banker's Trust where he made regular media appearances giving expert economic and financial commentary.
He moved to London in 1999, working at ill-fated investment bank Lehman Brothers, before starting Penrich in 2004 and returning to New Zealand a decade later where he became a fixture in Canterbury football and Cashmere school boards of trustees.
Until the collapse of Penrich Tonkin was well-known and respected in financial circles.
The charges he faces all carry a maximum sentence of 10 years in prison.
