Cryptocurrency trading firm Cryptopia has told customers its bank is closing one of its accounts.
The company said the bank's move had come at very short notice and with little opportunity for the company to present its case and provide compliance documentation.
It is understood that the company had been banking with ASB Bank.
An ASB spokesperson said they could not comment on specific customers, but said the bank was reviewing its relationships with crypto-exchanges to ensure they complied with regulatory obligations.
"Like all banks, and other industries, ASB is operating in a complex regulatory environment (globally and locally) with anti-money laundering and counter-terrorism financing laws, among the range of regulations with which we have to comply," the bank said.
"Ultimately, our goal is to keep our customers safe."
As a result, Cryptopia said it was halting deposits to its NZDT account until it had resolved the issue.
NZDT is used by New Zealand traders as a way into, and out of, cryptocurrencies on Cryptopia.
Cryptopia general manager Dave Sanders said it represented less than two per cent of the trading on its platform.
"While we are working hard to secure alternative banking services, we have to prepare for the possibility that there may be a period of time between this closure and being able to provide these services again in future," the company said on its website.
"Rest assured, Cryptopia is committed to ensuring our users remain the top priority and have access to their funds at all times."
Sanders said he could not comment on the bank's reasoning for withdrawal, but Cryptopia was talking to its bank, as well as others.
"We are focused on securing lasting and open relationships with bank providers so that this will not happen again in future," he said.
"While some exchanges choose to operate by opening bank accounts without being transparent, and running these until they get shut down, we believe this exposes us and our customers to greater risk and uncertainty."
Sanders said the company was working with government regulators, and had told customers about the account issue in a bid to be open and transparent.
Almost a month ago, Cryptopia suspended trading in two of its base markets, the Doge and Litecoin (LTC) currencies, saying it could not handle the number of trades.
Co-founder Rob Dawson blamed the high number of registrations and scaling issues for the trading halt.
"By the 1st of December we hit 500,000 users. On the 31st of December we hit 1,000,000 users. By the 3rd of January we hit 1,100,000 users. By the 4th of January, even with registrations disabled for three hours, we hit 1,200,000 users."
Sanders said trading was still halted in LTC and Doge while the company sorted further infrastructure. He said both should open again soon.