What was the 1945 document that formally ended Japan’s war with the Allies called?

The document was called the Japanese Instrument of Surrender.

It was the printed agreement through which Japan formally capitulated to the Allied powers on 2 September 1945. Japanese representatives signed it aboard USS Missouri in Tokyo Bay, followed by representatives of nine Allied governments.

The Instrument required Japan to accept the provisions of the Potsdam Declaration, which had demanded Japan’s unconditional surrender in July 1945. The Potsdam Declaration was therefore an ultimatum, not the document that recorded the final capitulation.

The Instrument also directed Japanese forces to cease hostilities and surrender according to instructions from Allied commanders. Its signing followed the 15 August announcement by Emperor Hirohito, but it provided the formal legal and military conclusion to the war. The later Treaty of San Francisco, signed in 1951, was a separate peace treaty that formally ended the state of war between Japan and many Allied countries.