The Japanese social security pension system is a two-tiered structure consisting of a basic program called the National Pension (NP), and four supplementary earnings-related programs, the most important of which is called the Employees' Pension Insurance (EPI). The NP, or first tier, is a contributory program that covers all residents of Japan. The EPI program covers workers employed in firms with at least 5 employees, while the three smaller second-tier earnings-related programs cover distinct occupational groups under government-sponsored mutual aid societies. Unless the context requires otherwise, references in these annotations to the EPI encompass all four second-tier programs.

As indicated in Article 2.1(a), both tiers of Japan's two-tiered pension system are included within the scope of the Agreement. However, several components of this system are excluded. The National Pension Fund and the Employees' Pension Fund are corporate pension funds under which both participation and contributions are voluntary. The Japanese Government does not exercise control over these private funds, which are intended to supplement the public, two-tiered system. The pension system for members of local assemblies, a supplemental pension system for local government workers, has also been excluded from the scope of this Agreement. The Agreement does not apply to the Old Age Welfare Pension or to other Japanese non‑contributory, means‑tested allowances paid from general revenues.