Toss Transfer Outage Causes “Money Duplication” as Failed Transfers Are Withdrawn in Cash

1. Overview

For about 30 minutes on the afternoon of October 7, 2026, a system error caused money sent from other banks to Toss Bank to be returned to the sender as a failed transfer while still being recorded as deposited in the Toss Bank account. The balance in the sending account remained unchanged while the receiving account’s balance increased. Reports described this as a so-called “money duplication” phenomenon, meaning that money had been copied.

The incident did not end as a mere display error because the increased balance could actually be used. When the extra money was sent to another bank, the transfer went through, and repeating the same process caused the balance to keep growing. This immediately raised the question of how the bank would recover the money that had been deposited by mistake.

2. How the Error Came to Light

The issue first became known through a tip received by the Gangwon Domin Ilbo. At around 2:30 p.m. that day, the tipster sent 500,000 won twice and 1 million won once—a total of 2 million won—from a Woori Bank account to Toss. Woori Bank marked all three transfers as failed and returned the money to the account, but Toss processed all three as successful deposits, increasing the balance from 9,394 won to 2,009,394 won.

The tipster then sent 1 million won of that amount to an IBK account, and the transfer reportedly went through, allowing the money to be withdrawn as cash as well. To restore the original amount, the tipster sent 1 million won from IBK back to Toss, but this time IBK again marked the transfer as failed, leaving the money there, while Toss received the 1 million won. The attempt to reverse the transaction had instead increased the balance once more. Toss customer support said there was an internal outage and that it was checking with the Korea Financial Telecommunications and Clearings Institute.

3. A Reporter Reproduces the Error

The Electronic Times reported that it reproduced the error itself that same day. When it sent 5,000 won in Naver Pay Money to a Toss Bank account, the Naver Pay app displayed the message, “The money transfer failed, so the transfer was canceled,” but Toss Bank received the 5,000 won, while the Naver Pay balance remained unchanged. After repeating the process three more times, the reporter had received 20,000 won without spending a single won.

This indicated that the problem lay with the receiving bank, Toss Bank, rather than with the sending bank or the mobile payment company. The Electronic Times also reported that the issue was confirmed to be an error at Toss Bank unrelated to Naver Pay. The error was determined to have lasted for about 30 minutes, from 2:20 p.m. to 2:50 p.m.

4. Toss Bank’s Explanation

Toss Bank issued a notice saying it had fixed the error as soon as it confirmed it and that all services were now operating normally. It attributed the cause to a software error during an internal system update. A representative explained that “a single transfer request was processed more than once, causing the error.” The bank said that incorrectly deposited transactions would be corrected in accordance with relevant laws and terms of service, and that the affected customers were being notified individually.

However, by the time of reporting, no action had been taken to recover the money that had been deposited by mistake. The Electronic Times reported that the Electronic Financial Transactions Act requires financial companies to investigate and resolve transaction errors immediately upon learning of them. It also noted that the Supreme Court had previously held that, absent special circumstances, a bank may correct a deposit record when money is credited to a customer’s account due to the bank’s mistake.

5. Authenticity debate

There are two main points of contention. One is whether the error was related to the hacking incidents that had affected the financial sector around the same time. The other is whether the bank can unilaterally reverse money that was deposited by mistake.

5.1. The view that it was a simple error, not a hack

Toss Bank explicitly stated that the incident was unrelated to an external attack or an AI-based hack that had breached its system. The error appeared only at the receiving institution and only for about 30 minutes during an update, while the bank’s explanation that the same transfer request was processed twice also fits the pattern. Since there is precedent allowing banks to correct deposits made by mistake, this side holds that the “duplicated money” would disappear once the records were corrected.

5.2. The view that it cannot simply be dismissed

The opposing view focuses less on the scale of the error than on how it is handled afterward. On March 10, 2026, Toss Bank also incorrectly applied a yen exchange rate of around 472 won per 100 yen—about half the previous day’s closing rate of 932.86 won—for roughly seven minutes, resulting in about 27.7 billion won being exchanged. The following day, it canceled the transactions all at once without customers’ consent. Complaints followed, arguing that customers had placed orders at the displayed exchange rate and that this therefore did not constitute an “error” under the Electronic Financial Transactions Act. The Financial Supervisory Service has asked the Financial Services Commission for a legal interpretation. Critics also point out that another large-scale system error occurred at the same bank barely six months later, that it remains unclear how money already transferred to other banks will be recovered, and that the number of affected customers and the total amount involved have not yet been disclosed.

6. Trivia

• The Gangwon Domin Ilbo noted that the outage occurred while hacking incidents had been confirmed at seven financial companies—Shinhan Bank, KB Kookmin Bank, Hana Bank, BNK Busan Bank, Yegaram Savings Bank, Welcome Savings Bank, and Hyundai Capital—and financial authorities were conducting emergency inspections of about 500 financial companies. It added, however, that no connection between the two events had been confirmed.
• The Gangwon Domin Ilbo wrote “Toss,” but reports from other outlets and a notice from Toss Bank indicate that the error affected Toss Bank accounts.
• This was not the first time the phrase “money duplication” had circulated in connection with the Toss group. In September 2022, a similar incident occurred when an incorrect exchange rate was applied to Toss Securities’ currency exchange service.