What was the formal document signed by Japan on 2 September 1945?

The formal document signed by Japan on 2 September 1945 was the Japanese Instrument of Surrender.

The instrument recorded Japan's acceptance of the surrender conditions and required Japanese forces to cease hostilities. Japanese Foreign Minister Mamoru Shigemitsu signed for the Japanese government, followed by General Yoshijiro Umezu for Imperial General Headquarters. Allied representatives then signed on behalf of the participating powers.

The ceremony occurred aboard the USS Missouri in Tokyo Bay and began shortly after 9 a.m. Japan Standard Time. The document was produced in two versions: one for the Allied powers and another for Japan. Its signing transformed the earlier announcement of surrender into a formal international act.

The instrument is sometimes confused with the Potsdam Declaration. The declaration, issued in July 1945, stated the Allied terms for Japan's surrender; the instrument signed in September documented Japan's acceptance of those terms.