The vast majority of New Zealand clients invested through Interactive Brokers, a "white label" digital wealth management platform enabling investors to trade in New Zealand dollars.
One investor who spoke to the Herald on condition of anonymity is kicking himself after investing close to $50,000 of his savings.
"I can't do much about it, that's the frustrating part of it all," he said.
"It's partly my own fault because they gave me a really low fee for each transaction compared to the banks. I guess you get what you pay for, but you still don't expect this to happen to a regulated stock broker.
"The only way is not to put all your money into one basket, I guess."
Exactly what went wrong at Halifax is a question the administrators are trying to establish.
But what is known is that they were appointed by Halifax's sole Australian director Jeffrey Worboys after the company's external auditor identified a shortfall in funds.
And it appears that the shortfall originated from Halifax Asia, a relatively new subsidiary that is not part of the administration.
"There are a significant number of investors based in Asia and in the days leading up to our appointment, a deficiency in those client accounts were identified by the external accountants," said Stewart McCallum, one of three Ferrier Hodgson partners appointed as administrators.
"We need to understand where the Chinese investors fit in to all of this."
The Herald can also reveal there have been concerns about Halifax's Australian operations in the past, with previous regulator warnings about the company's risk management and compliance framework.
Halifax Investment Services was established in 2001 in Sydney and expanded on the back of the global resources boom.
In 2013 Halifax started trading in the US but ceased trading shortly after when the regulator in charge of foreign exchange markets, the Commodity Futures Trading Commission, banned it from accepting American customers who weren't deemed eligible under new laws brought in following the GFC.
Meanwhile, the Australian Securities and Investments Commission was also monitoring Halifax closely. In April 2013 the regulator issued the company with an enforceable undertaking after a six-month investigation uncovered risk management and compliance flaws.
These included failing to adequately monitor its authorised representatives, failing to ensure staff were properly trained and adhered to professional standards, and failing to have an adequate complaints assessment and handling process.
An independent expert was appointed to monitor a plan to rectify the deficiencies.
The previous year, in 2012, Halifax New Zealand had commenced trading.
In June 2015 it gained a derivatives issuer license from the Financial Markets Authority, allowing it to transact a variety of financial products, including futures, options, foreign exchange and CFDs.
New Zealand managing director Andrew Gibbs, who owns the other 30 per cent of Halifax NZ, said at the time the need to meet stringent FMA requirements meant Halifax now had "world-class compliance and operating systems".
Gibbs did not return calls for comment on the administration.
But in a statement to clients last week he expressed surprise and dismay at what is now unfolding.
"Until Halifax was notified of the external administration action on Friday we had no information, foresight or knowledge to prepare or salvage the situation," he said.
Administrators are now focusing on untangling the mess, with McCallum saying he wasn't prepared to "sugar coat" what was likely going to be a lengthy, court intensive process.
"We've taken a forensic image of all the company's computer records, laptops and interviewed the director and staff.
"I'm not suggesting there's any fraud because we've only been in the seat for a week and a half. But what I am saying is there is a deficiency in investor funds of between 10 and 20 million based on our initial investigations."
The administrators were in daily contact with both ASIC and the FMA, he added.
