Friends who run factories for the Japanese market have nine times out of ten been stumped by PSE. When a customer's email says "please provide the PSE certificate," you ask around and some say you need the diamond mark, some say the round mark is fine, and others tell you "cables don't need it." Who are you supposed to listen to? First, let's be clear about what this certification governs: PSE is the mandatory certification under Japan's Electrical Appliance and Material Safety Law (DENAN Law), and it governs safety at the moment a product is connected to Japan's power grid—electric shock, fire, leakage, these things. It does not test performance, it does not test EMC, it only focuses on electrical safety itself. So don't try to fob it off with a CE LVD report—Japan does not recognize it.
Which products need it? There are two categories, and this is the first step where people most easily fall into a trap. Diamond PSE is for "Specified Electrical Appliances," which are high-risk and must be certified by a qualified assessment body registered in Japan, such as wires and cables, plugs and sockets, fuses, transformers, chargers, lithium batteries—116 types in total. Round PSE is for "Non-Specified Electrical Appliances," which are lower-risk and can be self-declared, but you still have to test according to the Japanese ministerial ordinance and keep records; most household appliances, LED luminaires, and power tools fall into this scope—341 types. Where's the trap? Many factories treat chargers as round, which is wrong—chargers are diamond; others treat products with lithium batteries as a whole as round, but in fact both the battery cells and the battery packs require diamond. Once the classification is wrong, the certificate is worthless, the goods are detained at customs, and you have no way to explain it to the customer.
The second trap is that "self-declaration" is understood as "no testing required." Round PSE indeed does not require third-party certification, but you must test according to the technical standards of the DENAN ministerial ordinance, and you must keep test records and certificates; the Japanese Ministry of Economy, Trade and Industry (METI) may come to inspect at any time. Quite a few factories just find a laboratory at random to issue a report and ship the goods, and the result is that the report items are incomplete or the standard version is wrong, and the customer rejects the order outright during audit. The third trap is the factory inspection for diamond PSE; the certification body will look at your production consistency and inspection equipment—it is not just a matter of sending a sample and being done. On timelines, for round PSE, if the materials are complete and testing goes smoothly, a report can generally be issued in two to three weeks; diamond PSE requires queuing, and adding the factory inspection, it is usually four to eight weeks, and if the body is busy or the product needs rectification, dragging on for two or three months is also normal. So don't wait until the customer urges you to act; figure out the classification in advance, match the test standards to the right version, and keep all the records you should keep—this saves far more trouble than patching holes afterward.