This functionality is only available to approved Introducing Brokers so please do not expect to use this functionality if you haven't been explicitly told that it will be available for you.
Initiating a request for pre-booking of funds
In scenarios where the transfer of physical funds does not happen immediately, a partner may call the POST /atr/v1/parner/prebookedfunds endpoint to advise Saxo that funding has been initiated by the client.
Saxo may - under some circumstances - use this information to credit the specified client account with the amount specified in the request. The client may then use the money to start trading immediately.
Saxo will reconcile such pre-booked funds requests with actual funds being received.
The reference documentation can be found here: Partner - Prebooked Funds.