The Japan Pension Service began assigning a set of fixed digits to the basic pension numbers of people with gender identity disorder last year, according to sources.

The four digits, which the pension service began to assign in October to distinguish individuals who have changed their gender designation, were contained in a pension consultation manual obtained and posted online by a third party, sparking criticism from GID individuals and their supporters who view it as a violation of privacy.

Each citizen has a 10-digit basic pension number, but under the new system in place since last year, those with GID were given the same first four digits, making it possible for employers to learn of their altered gender.

The agency said the new system was implemented to more accurately confirm the pension status of individuals before and after changes in gender designation, and to avoid mistakenly consolidating their two pension records.

The Japanese Society of Gender Identity Disorder said that around 3,000 to 4,000 people in the nation have changed their gender designation. After discovering the online leak in January, the pension service issued new basic pension numbers to around 200 GID individuals by April.