A buy instruction is created when a trade is placed outside of market hours* or during an intra-day auction. Your buy instruction will be converted into a buy trade when the market opens on the next trading day or once the intra-day auction has ended.
If you want to know how to set up a buy instruction, visit this FAQ - How to create a buy instruction?
While you have pending Buy Instructions, the purchase value of those Buy Instructions will be held by us in order to make the purchase when the market is open and will not, therefore, be available as free cash. If you want to access the cash, you will need to cancel the Buy Instructions, which you can do by following these instructions - How do I cancel a buy instruction?
*ZAR trading hours are between 09:05 and 16:40 Monday to Friday (excluding public holidays). ZAR trading will be closed on South African public holidays.
*USD trading hours are between 9:35 and 15:50 EST (16:35 and 22:50 local time and 15:35 to 21:50 during US Daylight Savings Time) Monday to Friday. USD trading will be closed on U.S holidays