The Diet passed a bill Thursday to expand the use of a personal identification number to improve tax collection, despite ongoing concerns over the potential leak of private information and identity theft.

Under changes to the so-called My Number system, personal ID numbers can be linked to people's bank account numbers from 2018. Although such links will be made initially on a voluntary basis, the government is considering making it mandatory from 2021.

The amendment will make it easier for the government to discover tax evasion or welfare benefits fraud by having better access to information on people's assets.

The revision will also expand the use of ID numbers to track records of vaccinations and health checks.

Under the My Number system, all residents, including non-Japanese, will be assigned a 12-digit identification number starting in October.

The government is set to start using the ID from January next year for administrative purposes such as taxation and social welfare benefits.

Meanwhile, the Diet also passed a bill to revise the law on private information protection, allowing companies to use personal data even without people's consent if the data is processed to ensure anonymity of information.

The change will allow companies to use massive amounts of personal information, dubbed "big data," for commercial purposes.

Under the law, the government will set up a committee in January next year to monitor the way companies are handling data, aiming to prevent leaks or abuse of personal information.

Fears still linger for some people over the possibility their personal information could be leaked following the recent massive leak of private data from the government-affiliated Japan Pension Service.

In that case, over 1 million people were affected.

The passage of both bills was significantly delayed due to the unprecedented leak scandal.