Stock orders amounting to more than the size of Sweden's economy were cancelled in Japan on Wednesday, in what could have turned into one of the biggest trading errors of all time.

At 9.25am Tokyo time, orders for shares in 42 companies totaling 67.78 trillion yen ($711 billion) were cancelled, according to data compiled by Bloomberg from the Japan Securities Dealers Association. A representative at the organisation wasn't immediately available to comment.

Billions of dollars worth of Japanese share trades have been reversed due to what appears to be one of the biggest trading errors ever. Credit:Reuters

The biggest order was for 1.96 billion shares of Toyota, or 57 per cent of outstanding shares at the world's biggest carmaker, for 12.68 trillion yen through an off-exchange transaction.

Toyota declined to comment. Other stocks with scrapped transactions included Honda, Canon, Sony and Nomura Holdings.