Which document did Japan accept when it surrendered in World War II?

Japan accepted the Potsdam Declaration when it surrendered in World War II.

The declaration was issued on July 26, 1945, by the United States, the United Kingdom, and China. It demanded Japan's unconditional surrender and warned of “prompt and utter destruction” if Japan refused. The Soviet Union later joined the declaration after entering the war against Japan.

Japan's government initially did not accept the Allied demand. After the atomic bombings of Hiroshima and Nagasaki, the Soviet declaration of war, and intense debate within Japan's leadership, Emperor Hirohito directed the government to accept the terms.

The Japanese Instrument of Surrender, signed on September 2, was the formal document that recorded Japan's capitulation. The Potsdam Declaration was the earlier Allied statement whose terms Japan agreed to accept, so the two documents are related but not interchangeable.