There are certain actions that can be perfomed when the Market is closed.  New orders - Orders cannot be placed outside market hours which is after 16:10 to 7:00 the next business day.  Certain amendments* and Cancellations are allowed  during the Adjust/On period between 16:12 and 18:50 (AEST). No other actions are permitted after 18:50. Amendments to orders that will not advance your order.  For example:  You have a Buy order in BHP for 100 @ $20.00.  You can amend to reduce your volume and/or lower your order price. You have a Sell order in BHP for 100 @ $20.00.  You can amend to reduce your volume and/or increase your order price.