A diamond PSE mark on an AC adapter is only the start: match the responsible business, certificate and type

Why does a plug-in adapter use the diamond PSE route?

METI divides 457 regulated electrical-appliance items into 116 Specified Electrical Appliances and Materials and 341 non-specified items. Its official overview names AC/DC power-supply units as a specified example. METI’s current scope-interpretation page describes the regulated DC power-supply-unit category as including units that also operate as AC supplies, generally with rated capacity up to 1kVA, while excluding certain specially constructed radio-communication test equipment.

Classification comes before document review. A USB wall charger, a power unit built into another product, a battery-powered device and a standalone DC supply may not be treated identically. Buyers should preserve the rated input, output combinations, capacity, plug and cord configuration, enclosure, intended use and relationship to the host product, then ask the responsible business to document why the exact item falls inside—or outside—the regulated category.

Who is legally responsible, and what does the certificate support?

Under the Act and METI procedure, a business that manufactures or imports covered electrical appliances must notify the government. For imported products, METI assigns the statutory duties to the importer: confirming technical conformity, conducting the prescribed self-inspection and keeping its records. Specified products also require conformity assessment by a body registered with METI. Only after the notifying supplier has fulfilled the relevant obligations may it place the statutory PSE marking on the product.

The assessment certificate belongs inside that system; it is not a transferable marketing badge. The buyer should identify the certificate holder or applicant, the registered assessment body, the covered product name and type classification, issue and validity information, manufacturing factory or facilities covered by the assessment, and any referenced technical standard. A retail model that is absent from the certificate may still be covered through a documented type classification, but that mapping must be shown rather than inferred from an enclosure photograph.

• Japanese notifying supplier and its legal role
• Registered conformity-assessment body
• Certificate number, issue date and current validity
• Covered product name and type classification
• Manufacturer, factory and assessed facilities
• Technical file connecting the retail model to the assessed type

What changed for overseas sellers, and what should the buyer match?

Since 25 December 2025, Japan’s amended product-safety framework also allows a qualifying overseas business that sells regulated products directly to Japanese consumers without a domestic importer to notify as a specified importer after appointing a domestic administrator. METI states that existing Japanese importers remain regulated as before. The new route does not make every overseas factory a notifying supplier; the actual sales and import structure determines which legal path applies.

A practical review therefore works from the transaction outward. Confirm whether a Japanese importer or a qualifying overseas direct seller is the responsible business, then match its identity to the notification route and final marking. Match the quoted adapter’s ratings, plug, connector, model suffix and type classification to the certificate and technical file. Finally, review the self-inspection record format and a current production record. This sequence separates a genuine market-access file from a correct-looking mark copied onto unrelated artwork.