Can a buy or sell transaction be reversed or cancelled? Can a buy or sell transaction be reversed or cancelled?

Can a buy or sell transaction be reversed or cancelled?

Only orders that have not executed yet can be cancelled. As soon as your order has executed, it cannot be cancelled or reversed.

Should you wish to change your open order, please refer to the steps in the article "How do I cancel or change an open order?". 

Recommendation:

Please be sure to always check your order before confirming it and to only submit orders that you actually intend to execute.