Shopify purchase orders: how to decide what goes on each one

Writing a purchase order is the easy part. The hard part, for most Shopify stores, is deciding what goes on it: which products, how many of each, and from which supplier, before the stock you have runs out. This guide covers both. It explains what a purchase order needs to contain, where purchase orders live in Shopify, and a weekly routine for working out the quantities, with an email template for sending the order.

What a purchase order is for

A purchase order (PO) is your written order to a supplier: what you want, how many, at what price, and when. It does three jobs:

• It tells the supplier exactly what to make or ship, so there is no argument later about quantities or prices.
• It records stock you are waiting for. Until it arrives, those units are "on order", and you should count them before ordering the same product again.
• It gives your bookkeeping a document to match against the supplier's invoice.

What to put on a PO

Keep one PO per supplier per order. Mixing suppliers on one document makes receiving and matching invoices harder.

Purchase orders inside Shopify

Shopify's admin has a purchase orders feature. According to Shopify's help center, a purchase order records the products, quantities, costs, payment terms and supplier details for an order. You can save it as a draft, mark it as ordered once the supplier confirms, and then use an inventory transfer to track the shipment and receive the stock.

That covers recording the order. It does not decide the quantities for you. The numbers on each line still have to come from somewhere, and that is where most of the weekly time goes. Check Shopify's own documentation for the current details, since admin features change.

Working out what to order

For each product, you need four numbers:

1. Daily sales. Units sold per day over the last four to eight weeks, leaving out cancelled and refunded orders. Shopify's orders export gives you the line items and dates to calculate it.
2. Stock available now. From Shopify's inventory export or the Inventory page.
3. Stock already on order. Units on POs you have sent and not yet received. Shopify's inventory export includes an Incoming column for stock on its way that you have recorded in Shopify.
4. The supplier's lead time. Days from sending the PO to having the stock on your shelf.

Then the rule is:

Order now if: (available + on order) ÷ daily sales < lead time + order cycle + safety days

Quantity = daily sales × (lead time + order cycle + safety days) − available − on order

The order cycle is how often you order from that supplier, for example every 7 days. Safety days are extra cover for delays; our safety stock calculator guide explains how to choose them. Round each quantity up to the supplier's case pack and minimum order.

A worked example

A candle store orders packaging weekly from a supplier with a 21-day lead time and keeps 7 safety days, so each order has to cover 35 days.

The thank-you cards show why stock on order matters. On the shelf alone they last 18 days, which would look urgent. Counting the confirmed order, they are covered.

The reorder point calculator guide has the same calculation as spreadsheet formulas.

A weekly routine

1. Monday morning, export. Inventory export (with Incoming) and the last 56 days of orders.
2. Calculate. Daily sales, days of stock left and quantity per product, as above.
3. Group by supplier. One draft PO per supplier with anything due.
4. Check the drafts. Look for anything odd: a product that was out of stock (its sales look low), a new product with no history, a promotion coming up.
5. Send and record. Send each PO, record it as ordered so it counts as stock on order, and note the expected delivery date.
6. Receive. When stock arrives, receive it against the PO so the on-order figure drops back.

A template for sending the PO

Attach the PO or paste the lines into the email body. Suppliers who receive many orders appreciate a clear subject line with the PO number.

Subject: Purchase order PO-1042 from [Your store]

Hello [Supplier contact],

Please find our purchase order PO-1042 below.

SKU            Item                    Qty     Unit cost
MAIL-KRAFT-M   Kraft mailer, medium    1,200   [price]
TISSUE-SAGE    Tissue wrap, sage       800     [price]

Deliver to: [Address]
Payment terms: [as agreed]

Could you confirm the quantities and the expected ship date?

Thank you,
[Name]
[Store] | [Phone]

Where Reorder Day fits

Reorder Day does the quantity work. For a Shopify store you upload two admin exports each week (inventory and orders, about two minutes), and every week it emails you a draft purchase order per supplier, based on each product's sales pace, the lead time you set for that supplier, and the stock on order from Shopify's Incoming or from POs you mark sent. You can edit quantities, download a CSV, print it, or open an email to the supplier from your own mailbox. It never sends anything to your suppliers itself.