If you have ever emailed a supplier "send me 500 units at $4 each" and called it a day, you have written an informal purchase order. The formal version just makes it official, unambiguous, and enforceable.
Here's what a purchase order actually is, what belongs on one, how it moves through your business, and how it fits into the reorder decisions that keep you in stock.
A purchase order (PO) is a formal document a buyer sends to a supplier requesting specific goods or services at an agreed quantity, price, and delivery date. Once the supplier accepts it, it becomes a binding contract. For a DTC brand, a PO is the document you generate the moment a SKU hits its reorder point.
What a purchase order is#
A purchase order is the buyer's side of a transaction, put in writing before any goods change hands. It states what you want, how many, at what price, and when you need it delivered. You send it to the supplier, and if they accept it, both sides are now bound to those terms.
That last part matters. A text message asking "can you get me 300 units" is a request. A PO with a number, itemized quantities, agreed pricing, and a signature or acceptance is a contract. If the supplier ships something different from what the PO says, you have grounds to reject it.
Most brands start with informal ordering (an email, a call, a text) and formalize into real POs once volume grows, once a bookkeeper needs a paper trail, or once a supplier relationship gets complicated enough that verbal terms stop being safe.
What's on a purchase order#
A complete PO has a consistent set of fields, whether it's a PDF, a form in your ERP, or a line in a spreadsheet:
- PO number. A unique identifier used to track the order and match it later to receiving and invoicing.
- Buyer and supplier details. Company name, billing address, shipping address, and contact information for both sides.
- Line items. SKU, description, quantity, and unit price for each product ordered.
- Total cost. Extended price for each line plus any shipping, tax, or freight terms.
- Delivery date and location. When the goods need to arrive and where.
- Payment terms. Net 30, net 60, deposit required, or whatever was negotiated.
- Shipping terms. FOB origin, FOB destination, or the Incoterm that applies if you're importing.
Miss a field and you create ambiguity that surfaces later, usually as a dispute over what was actually agreed to.
The purchase order process#
A PO moves through a predictable lifecycle. The steps look the same whether you're running a five-person brand or a company with a dedicated purchasing team.
- Identify the need. A SKU is running low, usually because it has crossed its reorder point, or a new product needs an initial production run.
- Create the PO. Fill in items, quantities, agreed pricing, and delivery date.
- Internal approval. Someone with budget authority signs off, especially above a spend threshold.
- Send to supplier. The supplier reviews and either accepts, rejects, or proposes changes.
- Supplier acceptance. Once accepted, the PO is binding. This is the point where lead time starts counting down.
- Goods shipped and received. You receive the shipment and check it against the PO's quantities and item numbers.
- Three-way match. The PO, the receiving record, and the supplier's invoice are compared before payment goes out. Mismatches get flagged before you pay for something you didn't receive.
Brands that pay invoices without checking them against the original PO and the receiving count are the ones that discover, months later, that they've been paying for quantities they never got. The three-way match is tedious, but it's the control that catches it.
Purchase order vs. invoice vs. sales order#
These three documents get confused constantly because they all reference the same transaction, just from different angles and at different points in time.
| Document | Who creates it | When | Purpose |
|---|---|---|---|
| Purchase order | Buyer | Before shipment | Requests goods at agreed price and quantity |
| Sales order | Seller | After receiving the PO | Confirms the seller will fulfill the order |
| Invoice | Seller | After shipment | Requests payment for goods delivered |
A PO and a sales order are mirror images of the same commitment, one from the buyer's side, one from the seller's. The invoice comes later and should reference the original PO number so accounting can match all three before releasing payment.
Types of purchase orders#
Not every order fits the standard one-time PO. A few variations show up often in e-commerce purchasing:
- Standard PO. A one-time order with a fixed quantity, price, and delivery date. This covers most reorders.
- Blanket PO. An agreement to buy a set quantity over a period (say, a quarter), with individual releases against it as you need stock. Useful when you have a stable demand forecast and want to lock in pricing without committing to one giant shipment.
- Contract PO. A longer-term agreement covering terms, pricing, and volume commitments, often used with a primary manufacturer.
- Planned PO. A tentative order with estimated quantities and dates, used for planning purposes before it's finalized into a standard PO.
Most small and mid-size DTC brands live almost entirely in standard POs, with a blanket PO occasionally used for a hero SKU with steady, predictable volume.
How purchase orders fit inventory planning#
A PO doesn't exist in isolation. It's the output of a decision your inventory planning already made. The chain looks like this:
- You track sell-through and calculate a reorder point for each SKU, per channel.
- When on-hand stock hits that number, it's time to order.
- You decide how much to order, often using an economic order quantity calculation that balances ordering costs against holding costs.
- You cut the PO and send it to your supplier.
- From the moment the supplier accepts, lead time starts. That's the clock your safety stock is there to cover, in case the shipment runs long or demand spikes while you wait.
- Once the PO ships, that inventory becomes "incoming stock." It's not on your shelf yet, but it should factor into any par level or reorder decision you make in the meantime, so you don't double-order.
The moment a PO is issued, its expected arrival date should feed back into your reorder math. Otherwise you risk placing a second PO for stock that's already on the water.
Getting this chain right, reorder point, order quantity, PO, incoming stock, is most of what separates brands that stock out or overbuy from brands that don't. Tracking inventory turnover over time tells you whether your PO sizing and timing are actually working.
See Enough Stock turn reorder points into ready-to-send purchase orders automatically
Common purchase order mistakes#
A few mistakes show up again and again in growing DTC brands:
- No PO number system. Without a consistent numbering scheme, you can't match invoices or receiving records back to the original order.
- Treating POs as optional for repeat suppliers. Verbal agreements with a supplier you trust still leave you exposed if pricing or specs shift.
- Not tracking incoming POs against reorder points. If your planning doesn't know a shipment is already inbound, you'll place duplicate orders.
- Skipping the three-way match. Paying invoices without checking them against the PO and receiving count is how quantity discrepancies go unnoticed.
The bottom line#
A purchase order is your formal, binding request for goods at a set price and quantity. It has a defined set of fields, moves through a predictable process from creation to three-way match, and sits at a different point in the transaction than a sales order or invoice. For inventory planning, treat it as the natural next step after a SKU hits its reorder point, and keep incoming POs visible so they factor into what you order next. If you want the reorder point to PO handoff to happen without spreadsheets, see how Enough Stock's platform tracks incoming stock and reorder triggers across every channel.