Stock management in PrestaShop 8 and 9: how it works

In PrestaShop 8 and 9, stock is managed per product or per combination (size, colour…), and each quantity is split into physical stock, stock reserved by orders not yet shipped, and stock available to sell. On each product you decide whether it can be bought when out of stock, and the catalogue's stock screen shows the quantities and movements.

It seems simple until a combination appears sold out with units on the shelf, or an order slips through without stock. This article explains how stock works in current versions, which settings control it and where it falls short. How to calculate the reorder point or sync stock across several channels is covered in other articles on the blog.

Enabling stock management

Under Shop Parameters, Product Settings, there is a stock section. The essentials:

• Enable stock management. If it is disabled, PrestaShop does not deduct units and everything can always be bought.
• Allow ordering of out-of-stock products, as the store's default behaviour. Each product can override it.
• Display available quantities on the product page, and the last-items warning below a certain quantity.
• Availability labels for when there is stock and when there is not, which can also be set per product.

Quantities per combination

When a product has combinations, the stock belongs not to the product but to each combination. The product's quantity is the sum of its combinations' quantities, and it is each combination's quantity that decides whether it can be bought. A common mistake is to set the quantity on the product and leave the combinations at zero: the store says there is stock, but the customer cannot choose any size.

Packs have their own rule: you can choose whether selling them deducts the stock of the pack, of the products in it, or both. If the individual products are also sold separately, the usual choice is to deduct the products in the pack so you do not sell what you do not have.

Physical, reserved and available

PrestaShop keeps three figures for each product or combination:

When an order comes in, the available quantity drops immediately and those units become reserved. When the order moves to a status marked as shipped, the units also leave the physical stock. If the order is cancelled, they come back. That is why order statuses must be configured properly: a custom status with the wrong flags can stop stock from returning on cancellation or deduct it twice.

Stock movements

Every quantity change is recorded as a movement: those generated by an order and those you make by hand when editing the product. On the catalogue's stock screen you can see the quantities of all products, filter them, change them in bulk and view the movements with their date and source. It is the first thing to check when a quantity does not add up: there is almost always an order, a manual edit or an import that explains it.

Out-of-stock orders

Each product can deny out-of-stock orders, allow them or follow the store's default. Allowing them makes sense for products you manufacture or that the supplier delivers within a few days, as long as the product page clearly states the lead time. If you allow them, available stock can go negative: that is PrestaShop's way of telling you how many units you owe.

Low stock alerts

On each product or combination you can set a low stock threshold and ask to be notified by email when the quantity reaches it; that merchant alert is sent by PrestaShop's email alerts module, which must be installed and configured. The same module lets customers request a notification when an out-of-stock product is available again. Check that those emails arrive: it is common for them to be set up once and for nobody to check that they are still being sent.

Importing quantities

To update the stock of many products at once, PrestaShop lets you import a CSV of products or combinations with the quantity column, identifying each row by its ID or its reference. Before importing into the live store:

• Back up the database.
• Test with a few rows and check the result.
• Make sure references are unique; if they are repeated, the quantity may end up on the wrong product.
• Bear reserved orders in mind: the quantity you import is either the one you want available or the physical one, and they are not the same.

If stock comes from an ERP or a supplier every day, the sensible option is an automatic connector, not a manual import.

Common mistakes

• Custom order statuses created without checking whether they count as shipped or cancelled.
• Combinations created in bulk that stay at zero while the product shows stock.
• Manual quantity adjustments without noting the reason, which nobody can explain later.
• Accepted returns that do not restock because nobody does it when the parcel arrives.

What happened to the advanced stock management of 1.6

PrestaShop 1.6 had advanced stock management, with several warehouses, cost prices per receipt, supplier orders and transfers between warehouses. Since 1.7 that feature is no longer part of the core: stock is once again a quantity per product or combination with its movements. If you are coming from a 1.6 store that used warehouses, when migrating you have to decide how that will be handled now, because it is not carried over as is.

When you need to forecast purchases

PrestaShop tells you how much you have, not how much you are going to need. For that you have to look at the sales over a period and compare them with stock and with the supplier's lead time. The sales average is misleading: if a product sold out on the first day and you took a hundred days to restock it, the average says it sells one a day, when in fact it could not be bought. You need something more when:

• You buy from several suppliers with different lead times.
• You have seasonal products or major campaigns.
• Products that sell well run out while what does not sell piles up.

How to solve it in PrestaShop

Rekire's stock requirements calculation module calculates how many units you will need up to the date you choose, based on sales over the period you set, filtering by supplier. From the moment it is installed, it records the days each product was out of stock or disabled and leaves them out of the average, so the daily demand is the real one. For each product and combination it shows the average demand, the units to add on top of current stock, sales and orders, with supplier reference and cost price, and it exports the requirements to CSV so you can take them to your spreadsheet or your ERP. It is compatible from PrestaShop 1.7.3 up to 9. Forecasting purchases in time costs less than losing the sales of a sold-out product.

Frequently asked questions

Why does a product appear out of stock if it has units?

Almost always because the units are on the product and not on its combinations, or because they are reserved by orders not yet shipped. Check each combination's quantity and the stock movements.

How do I avoid selling out-of-stock products in PrestaShop?

Enable stock management and deny out-of-stock orders by default, and review the products that override it. If you also sell on other channels, sync the quantities.

Does PrestaShop 8 or 9 have warehouse management?

Not like the advanced management of 1.6. The core keeps one quantity per product or combination; several warehouses or locations need a module or an ERP.

When is stock deducted in PrestaShop?

Available stock drops when the order is created; physical stock, when the order moves to a status marked as shipped. If it is cancelled, the units come back.