Head to the ‘Inventory’ section of your Product Listing page. Check the box to “Enable product stock management”. This will bring up 3 options:
Enter the number of units you would like to sell. For example, if you choose 5, after the product has been purchased 5 times it will be automatically marked as “out of stock”
Low stock threshold
Select the number of units remaining to trigger an email notifying you that this product is close to selling out. You can then add more units to the stock quantity of you want to increase the potential number of sales
Allow back order
This allows buyers to purchase your product even if it is marked as “out of stock”. The buyer will then be notified by email when you have updated the stock quantity to be back in stock
Below the product stock management options, you can also check the box to “Allow only one quantity of this product to be bought in a single order”. This will limit the buyer to only one sale of your product at a time.