The Commonwealth Bank of Australia (CBA) has confirmed some credit transactions have been declined country-wide on Tuesday morning.
The issue is affecting those using Visa credit cards, a spokesperson told ZDNet.
"We are aware some Visa credit cards are declining this morning. Customers may be able to use Visa Debit by inserting their card and using 'Chip and PIN' by selecting savings or cheque," bank said.
"Eftpos, MasterCard, AMEX, and Diners are working as normal."
The bank took to Twitter on Tuesday morning following reports from customers unable to use their CBA-issued Visa card.
"We're aware of an issue affecting some Visa cards. We're working on this as a priority and apologise for any inconvenience. We'll continue to give you updates here," CBA posted.
Two and a half hours later, the bank posted another update that told customers they may be able to use the chip function on their Visa card instead.
"We apologise to our customers and we're working to restore services as soon as possible," the spokesperson added.
In early April the bank issued an apology for the "intermittent issues" its systems experienced, after customers of the bank were left without access to their credit card and loan information on the online banking platform.
The apology from CBA came almost 24 hours after customers reported issues with the bank's online system.
For the first half of the 2018 financial year, CBA reported AU$4.9 billion in after-tax profit on revenue of AU$21.3 billion.
The bank counts 6.4 million of its 15.9 million customers as "digital" customers, boasting 6.3 million daily logons to either the CommBank app or NetBank platforms. The CommBank app also has 4.8 million unique users, the bank reported, with each logging in at least once during December 2017.
According to CBA, 56 percent of its total transactions by value are digital, likewise 26 percent of retail sales are also digital. Mobile logins also increased by 25 percent in the last 12 months.
Last week, the bank said it was unsure of where data on millions of customers has gone, after it was revealed that magnetic tapes comprising information used to print account statements may not have been properly disposed of.
In May 2016, the bank was unable to confirm that two magnetic tapes containing information used to print account statements were securely disposed of following the scheduled destruction by a supplier.
The bank affirmed the tapes did not contain PINs, passwords, or other data that could enable account fraud.
The bank didn't alert customers, as the tapes containing the data were 'most likely' disposed of, rather than lost.
The bank has admitted it was late in filing more than 53,500 reports as required under the Anti-Money Laundering and Counter-Terrorism Financing Act, but has asked for Austrac to consider them as one course of conduct, arguing that it was due to one systems-related error.
Using technology, the banking heavyweight wants to get to know its customers better by restoring the relationship people had with banks over 40 years ago.
The bank's head of blockchain has revealed the Commonwealth Bank is currently implementing with a large world issuer in what will be a 'world-first' issuance of a bond on the blockchain that it hopes to bring to market in 2018.