Largest personal info leak revealed since 'My Number' system introduced

KOSAI, Shizuoka -- The ID numbers of 1,992 individuals under the taxation and social security system have leaked to third parties in what is believed to be the largest incident of this kind, it has been learned.

The Kosai Municipal Government notified 174 municipalities in Tokyo and seven other prefectures last month that 5,853 of their residents donated part of their taxes to the city under the "benefit-your-locality" tax scheme. Under the system, taxpayers can choose to divert part of their residential tax to a specified local body to help vitalize local economies.

However, the municipal government admitted on Feb. 16 that the city erroneously wrote down the 12-digit ID numbers of other individuals for 1,992 of the donors in its notification documents sent to local bodies in areas where these taxpayers' reside. An ID number has been given to each taxpayer under the Social Security and Tax Number System that was launched in October 2015.

The Personal Information Protection Commission (PPC) said it is the largest such incident since the scheme called the "My Number" system, was launched. The commission recognizes the case as a serious incident under the legislation regulating the ID system.

The municipal government claims that the possibility is slim that the information will further leak to outsiders.

Still, the PPC is poised to instruct the municipal government to conduct an in-house probe into the incident and draw up measures to prevent a recurrence.

Kosai Mayor Takeshi Kageyama apologized for the incident. "I'm sorry that we betrayed the goodwill of donors across the country," the mayor told a news conference.

The PPC regards cases in which the ID numbers of at least 100 taxpayers have been leaked and the computer network managing the Social Security and Tax Number System was illegally accessed as serious incidents under the legislation regulating the system.

In the first half of fiscal 2016, two such serious incidents were reported, including a case in which a private business had the ID numbers of about 400 individuals stolen.

The Kosai Municipal Government received a report from one of the municipalities on Jan. 30 that the wrong person's ID number was recorded in the notification, prompting the city to launch an investigation. The city subsequently confirmed that it had notified the 174 municipalities of other people's ID numbers for 1,992 of the donors.

Three officials at the Kosai Municipal Government compiled the notification documents. A mistake was made when they rearranged the list of donors on a computer.

Kazuyoshi Iida, general affairs manager at the municipal government, explained that the mistake is attributable to an increase in the amount of clerical work because it became compulsory from this year to enter ID numbers of the donors in the notification documents.

The city will send a letter of apology to the 5,853 donors, and introduce a new system to prevent a recurrence.