With the My Number law taking effect Monday, the government has kicked off the controversial personal identification system to unify the administration of every resident's official services and records, and will start sending numbers out to tens of thousands of households.

The numbers, which take effect in January to hopefully enhance the efficiency of administrative services, including taxation and the provision of social welfare benefits, are expected to reach some 55 million households on a tsuchi kaado (notification card) bearing 12 digits through registered mail between mid-October and the end of November.

Preparations for the system have been years in the making and have faced strong public resistance. The government is under pressure to handle the numbers carefully amid concerns that personal information could be leaked via use of the ID numbers.