What was the official name of Japan's document of surrender in 1945?

The official name of Japan's document of surrender in 1945 was the Japanese Instrument of Surrender.

The document was signed aboard USS Missouri in Tokyo Bay on September 2, 1945. It stated that Japan accepted the terms of the Potsdam Declaration and formally surrendered the Japanese Imperial General Headquarters, the armed forces, and territories under Japanese control.

Mamoru Shigemitsu signed for the Japanese government, followed by General Yoshijirō Umezu for Imperial General Headquarters. Douglas MacArthur accepted the surrender for the Allied powers, and representatives of eight other Allied nations added their signatures.

The Instrument of Surrender is different from the Potsdam Declaration. The declaration was an Allied demand issued in July; the instrument was the formal document that recorded Japan's acceptance and ended the war legally and ceremonially.