What was the official document signed at Japan's formal surrender ceremony in 1945?

The official document signed at Japan's formal surrender ceremony was the Japanese Instrument of Surrender.

The document was signed aboard USS Missouri in Tokyo Bay on September 2, 1945. It recorded Japan's acceptance of the terms proclaimed by the Allied powers and ordered the unconditional surrender of Japanese military forces. Japanese and Allied representatives signed separate copies.

The Instrument required Japanese forces to cease hostilities, surrender weapons, and carry out the orders of the Supreme Commander for the Allied Powers. It therefore functioned as a formal military surrender document rather than a comprehensive peace treaty.

The Potsdam Declaration was the Allied statement of surrender terms issued before the ceremony, so it is not the document signed aboard Missouri. The Treaty of San Francisco, which came into force in 1952, later ended the formal state of war between Japan and many Allied countries and restored Japan's sovereignty.