For foreign residence in Japan about MY NUMBER SYSTEM from Oct.

The social security  and Tax number system

The Japanese government will adopt the Social Security and Tax Number System in order to

(1) enhance the social security to people who truly need it,

(2) enhance public convenience and

(3) develop the efficiency in administration.

for more details,

http://www.cas.go.jp/jp/seisaku/bangoseido/pdf/en1.pdf