Most Shopify merchants reorder inventory when they notice something is running low. Here is how to build a system that tells you exactly what to order, when, and how much — before you ever hit a stockout.
Here is how most Shopify merchants manage purchase orders:
They check their inventory every few days. Something looks low. They email their supplier. The supplier replies in 48 hours. The PO gets created in a spreadsheet. It gets lost in an email thread. Three weeks later they wonder why the stock has not arrived.
Then they run out. Then they emergency-order at a higher price. Then they overcompensate and order too much. Repeat.
This is not a systems problem. It is the absence of a system.
The core issue with manual purchase orders is that every step depends on a human noticing something and taking action.
There are dozens of SKUs that need reordering at any given moment. No one checks all of them consistently. The ones that run out are the ones that fell through the attention gap.
The goal of automated purchase orders is not to remove human judgement from buying decisions. It is to ensure that the right information surfaces at the right time — so you are making deliberate decisions rather than reactive ones.
Before you can automate purchase orders, you need a reorder point for each SKU.
Reorder Point = (Average Daily Sales × Lead Time in Days) + Safety Stock
When inventory drops below this threshold, a purchase order should be triggered. Not when stock hits zero — when it hits the reorder point. The difference is the lead time cushion.
Example: - Average daily sales: 12 units - Supplier lead time: 14 days - Safety stock: 50 units - Reorder Point = (12 × 14) + 50 = 218 units
At 218 units remaining, you place the order. By the time stock arrives (14 days), you have exactly your safety buffer remaining.
This is the one step that requires manual work upfront. For each SKU, calculate: - Average daily sales (from Shopify sales data, last 30–90 days) - Supplier lead time (ask your supplier; track it over time) - Safety stock (use the formula from our safety stock guide)
For stores under 50 SKUs, a spreadsheet works. Above that, the maintenance burden becomes unsustainable.
Shopify has a built-in low stock alert you can configure per product. Set it to your reorder point, not zero.
The problem: Shopify's native alerts are per-product, not per-supplier. If you have 15 products from one supplier, you get 15 separate alerts at different times, and you are placing 15 separate small orders instead of one efficient combined order.
This is the step most merchants miss. An efficient PO system consolidates all low-stock items from the same supplier into a single order. This: - Reduces shipping costs (you pay freight once, not 15 times) - Gives you negotiating leverage (larger order, better terms) - Reduces administrative overhead for your supplier
When Supplier A has five products below reorder point simultaneously, the system should create one PO for all five — not five separate POs.
The recommended order quantity for each SKU is:
Recommended Qty = (Forecast demand during lead time + Safety stock) − Current stock
This accounts for what you will sell while you wait for the order, plus your buffer, minus what you already have.
Example: - Forecast demand over 14-day lead time: 168 units (12/day × 14) - Safety stock: 50 units - Current stock: 95 units - Recommended order qty = (168 + 50) − 95 = 123 units
Round up to the nearest supplier pack size or minimum order quantity.
A well-designed automated PO system does the following:
Most merchants currently do steps 1–8 manually, spread across Shopify admin, a spreadsheet, and an email inbox.
Supplier MOQs complicate automated ordering. If a supplier requires a 200-unit minimum but your reorder quantity is 80 units, you have three options:
Option 1: Inflate the order to MOQ Order 200 units. You will hold 120 units of excess stock for longer than optimal. Acceptable if the product moves reliably.
Option 2: Wait until multiple SKUs from the same supplier hit reorder Delay the order and bundle several products to reach the MOQ collectively. Requires careful tracking to ensure you do not stockout while waiting.
Option 3: Negotiate the MOQ Many suppliers will reduce MOQs for established, reliable customers. A track record of consistent orders is worth negotiating with.
Automated PO systems create a data trail that lets you track supplier reliability over time:
| Metric | What It Measures |
|---|---|
| On-time delivery % | Orders received by promised date |
| Fill rate | % of ordered units actually received |
| Lead time accuracy | Actual vs quoted lead time |
| Defect rate | % of received units with quality issues |
After 6 months of data, you can see which suppliers are reliable and which routinely ship late or short. This directly informs your safety stock levels — unreliable suppliers need larger buffers.
A well-structured PO template includes:
Sending this consistently (rather than informal emails) signals professionalism to suppliers and reduces errors on their end.
CoreCaptain generates formatted PO documents automatically — including the ability to email them directly to your supplier with one click. Received quantities are reconciled against the PO when you mark items as received, and any discrepancies are flagged automatically.
The real value of a systematic PO process is not in any single order. It is in the compound effect over a year:
Each improvement feeds the next. The merchants with the most accurate inventory are not necessarily smarter — they have better systems that make accuracy the default outcome.
Automating purchase orders does not mean removing humans from the process. It means ensuring humans are spending their time on decisions, not on data gathering.
Build your reorder points. Group by supplier. Let the system surface what needs ordering. Let a human review and approve. Let the system send, track, and reconcile.
That is the whole system. It is not complicated — it just requires building it once.
CoreCaptain detects phantom stock, sync errors, and inventory discrepancies automatically. 14-day free trial, no credit card required.
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