Here are the mandatory parameters needed for this call:

orders=[{
"Source": "sample string 7",
"SubSource": "sample string 8",
"ReferenceNumber": "sample string 11109590",
"ReceivedDate": "2017-04-19T14:18:36",
"DispatchBy": "2017-04-19T09:18",

"OrderItems": [{

        "TaxCostInclusive": true,

        "UseChannelTax": true,

        "PricePerUnit": 3.1,

        "Qty": 4,

        "TaxRate": 5.1,

        "LineDiscount": 6.1,

        "ItemNumber": "sample string 7",

        "ChannelSKU": "sample string 8",

        "IsService": false,

        "ItemTitle": "sample string 10"
}]
}]&location=default

There should be at least one item or service in the order. Above example does not have order item options field but you can check this link for available fields.

Please keep in mind that passing same source, subsource and reference number to an unpaid order will update it rather then create a new order.

For further information on datatypes please see the following documentation:

http://apps.linnworks.net/Api/Class/linnworks-spa-commondata-Order-ClassBase-Channel-ChannelOrder