What it was
MtGox Co., Ltd. was a Tokyo company that ran a bitcoin exchange at mtgox.com. Its customers deposited yen, dollars and bitcoin with it, traded, and withdrew. That is the whole model, and it is also the whole failure: the exchange held the coins, so the customers did not.
What happened
On 25 February 2014 the site closed. Three days later the company filed for civil rehabilitation at the Tokyo District Court. Its own filing, signed by representative director Mark Karpelès, put total assets at JPY 3,841,866,163 against current liabilities of JPY 6,501,119,371, and stated that an internal investigation had found that "approximately 750,000 bitcoins deposited by users and approximately 100,000 bitcoins belonging to us had disappeared". The company said it believed the coins were stolen through abuse of a bug, and reported a further discrepancy of about JPY 2.8 billion between customer deposits and cash held at banks.
The rehabilitation did not survive. On 16 April 2014 the Tokyo District Court dismissed the application, ruling that the company could not carry it out, and appointed Nobuaki Kobayashi as provisional administrator; bankruptcy followed. In June 2018 the court reopened civil rehabilitation, and a plan became final and binding on 16 November 2021. Repayments in bitcoin and bitcoin cash began in 2024. The trustee has since moved the repayment deadline twice, most recently to 31 October 2026.
On the record
The company's own 28 February 2014 filing at the Tokyo District Court is the primary record of the loss and the insolvency, and the trustee has published the court's orders since.
On 15 March 2019 the Tokyo District Court convicted Karpelès of falsifying the company's electronic records and sentenced him to two and a half years in prison, suspended for four years. The same court acquitted him of embezzlement and aggravated breach of trust, the charges prosecutors had led with. He said afterwards that he was "happy to be judged not guilty for embezzlement and breach of trust".
Listing here is not endorsement.