Firstly, you need to set up the Stock Rules for your shop – what you want to happen available products dip below a certain level or go out of stock.
Stock Rules are set by selecting the root/top category of the shop in Shop tab and clicking on the "Stock Control" tab then the task: "Create new stock rules for items in this category and below"
The default setup shown here does the following:
"Keep selling products until there is zero stock left, then stop allowing people to buy the product. Instead of showing e.g. '12 in stock', show 'Out of stock' on the product page. Keep displaying the item in the store."
Here's a more extensive example:
In this scenario, there's another message which displays when stock us getting low (between 1 and 5 items left) – it shows the message "Limited Stock" encouraging people to buy before the item sells out.
Secondly, if using stock control in your store, you can choose which products (items) use the stock control functionality.
On the "Details" tab of the product select "Use stock control for this item." You'll then be able enter a figure in the "Current stock on hand" field. The shop will now keep track of the number of items being sold and reduce the stock number accordingly. Don't forget to Save the changed settings.
In this example, there are 5782 copies of this book available to sell but 2 are earmarked in orders received which are yet to be processed. (5,782 minus 5,780 = 2).
When stock levels change, Item (product) visibility can be changed to "Everyone / Site Members / No one" in the stock rules setup screen.
You can set the item to be moved to another store category when stock is low, for example, you could have a category, "Selling out fast!" where products were moved when they dropped below a certain level.
As well as setting Stock Rules on a shop-wide basis as described above, Stock Rules can be set for a specific category of items by selecting that category first. They can also be set differently for individual items via the Stock Control tab of a specific item.