Pending orders can be edited or cancelled from the Order Status page on both the mobile app and website.
Note: Orders for NASDAQ-listed stocks cannot be modified or canceled between 9:25 AM and 9:30 AM ET, in accordance with NASDAQ regulations. To help prevent unintended executions, ensure any changes or cancellations are submitted before 9:25 AM ET.
Mobile app:
Select Order Status at the bottom of the screen
Select the order you wish to edit or cancel
Website:
Go to Trading -> Order Status
Select “Edit” or “Cancel” on the right-hand side
There are no fees associated with editing or canceling an order.