V9 - Drop-shipped purchase orders
SOS Inventory supports drop-shipping items directly from a vendor to a customer. To issue a drop-ship PO, simply check Drop ship on the purchase order and then select the intended customer from the dropdown in the Shipping address block.
On the Items list, the On PO quantities of items on drop-ship POs are not included in the calculation, as they are not incoming inventory. When you receive confirmation from the vendor that the items have shipped, update the PO with tracking information (if so desired) and then close the PO.
As long as you have set up your items correctly (where the expense account in QuickBooks Online is the COGS account), then you could do a copy to bill in QuickBooks Online, as that bill will affect accounts payable and COGS directly.
In Purchasing settings, the option Automate drop ship purchase orders (Tools & settings > Configuration > Purchasing > Purchase orders) closes a drop-ship PO automatically and sends journal entries to QuickBooks Online that post against accounts payable and COGS.
See Drop shipment workflows for examples of how you can process drop shipments in SOS Inventory.