A back-to-back order is a sales order line that is fulfilled by a purchase order created specifically for it, rather than from on-hand stock. In Acumatica this is not a bolt-on customization — it is built into the requisition and replenishment machinery, driven by the Replenishment Source on the non-stock or stock item and by the purchase-order link the system records on the sales order line. Understanding which field controls what saves you from writing automation for something the platform already does.
Drop-ship versus special-order (mark for PO)
Acumatica gives you two distinct back-to-back modes, and they behave differently downstream. A Drop-Ship line generates a purchase order whose vendor ships directly to the customer; there is no receipt into your warehouse and no shipment from it — the PO receipt is what closes the sales order line. A Mark for PO (special-order) line generates a purchase order that receives into your own warehouse, and the goods then ship to the customer on a normal sales shipment. Both are set on the sales order line through the PO Source field, but the fulfilment path, the inventory transactions, and the costing all differ.
| Drop-Ship | Mark for PO (special order) | |
|---|---|---|
| Goods flow | Vendor → customer directly | Vendor → your warehouse → customer |
| Inventory receipt | None (PO receipt closes the SO line) | PO receipt into warehouse, then SO shipment |
| SO line closed by | PO receipt | SO shipment + invoice |
| Typical item | Non-stock or stock | Stock item |
Where the link is configured
The trigger lives on the sales order line. On the Sales Orders (SO301000) screen, expand the line detail and set PO Source to Drop-Ship or Purchase to Order. For the automation to generate a PO, the item needs a valid vendor: either a default vendor on the stock/non-stock item, or a vendor picked when you run Create Purchase Orders. The item's Replenishment settings and the warehouse determine defaults, but the per-line POSource value is what actually marks the line for procurement.
Acumatica records the link in POLineType / SOLineSplit plus the POCreate tables. You rarely touch these directly — the point is that the sales order line and its purchase order line hold a mutual reference, so quantity changes, cancellations, and receipts propagate. Editing the PO quantity below what the SO reserved is what breaks the link, not the other way round.
Generating the purchase order
Once lines are marked, the purchase orders are created from Purchase Orders → Create Purchase Orders (PO505000), or automatically at sales-order save if the order type is configured to auto-create. The processing screen groups eligible SO lines by vendor and warehouse and produces one PO per vendor. For drop-ship, the PO's ship-to defaults to the sales order's shipping address rather than your warehouse — that substitution is the single most important thing to verify on the first go-live, because a wrong ship-to on a drop-ship PO means the goods land at your dock instead of the customer.
Order type configuration
Whether a line can be back-to-back at all is gated by the Order Type (SO201000). The order type's template controls whether PO link is allowed and whether drop-ship is permitted. If the Mark for PO option is greyed out on a line, the order type — not the item — is usually the reason. Keep a dedicated order type for drop-ship business if your process differs enough; it keeps the automation predictable and the reporting clean.
Receipt and invoicing behaviour
For a drop-ship PO, running Purchase Receipts against it closes the linked sales order line and makes it available for invoicing to the customer — you never create an SO shipment. For a special order, the PO receipt puts stock into the warehouse and allocates it to the reserved SO line; you then create the sales shipment normally. The cost that lands on the SO line comes from the PO receipt, which is why the customer invoice for a drop-ship item should be produced after the receipt if you want accurate margin on the first invoice.
If a customer cancels a back-to-back line after the PO is placed, cancel or reduce the purchase order first, then the sales order line. Cancelling the SO line while an open PO still references it leaves an orphaned PO that no longer knows who it was buying for — and Acumatica will not auto-cancel the vendor commitment for you.
When customization is actually warranted
Most teams try to automate the SO→PO creation and discover Acumatica already does it. The genuine customization cases are narrower: auto-selecting a vendor by rules more complex than the item default (for example, cheapest vendor for the requested quantity), stamping the customer PO number onto the vendor PO for drop-ship traceability, or blocking invoicing until the drop-ship receipt posts. Each of those is a small graph extension on SOOrderEntry or POOrderEntry — not a reimplementation of the workflow. Reach for the platform's built-in link first and extend only the decision you actually need to change.
Wrapping up
Back-to-back ordering in Acumatica is configuration before it is code: POSource on the line, a vendor on the item, and an order type that permits the link. Get those three right and the platform keeps the sales order and purchase order synchronized through receipt. Save the customization budget for the one decision your business makes differently — usually vendor selection or invoice timing. If you are stuck on a specific drop-ship edge case, reach out or keep reading through the rest of the Acumatica blog.
Independent software engineer in Nairobi specialising in Acumatica customisations, Laravel backends, and tax fiscalisation integrations across East and Southern Africa.