Define how you want to work with your stock in your osCommerce store in the "Stock" section of the configurations. You can define:
- Check stock level - have the store check for sufficient stock
- Subtract stock - have the store subtract stock as it's ordered by customers
- Allow checkout - allow customers to checkout even if there is not sufficient stock
- Mark product out of stock - place a visible marker on the page when it is out of stock
- Stock re-order level - when a re-order should be placed
