Using Magento 1.7.x for your clients online stores have the same numbers for; invoice, shipment, and credit-memo? Try this little gem ‘Fooman Invoice=Order Number’, a free extension for Magento. Instead of keeping separate counts for invoice, shipment, and creditmemo numbers, this plugin uses the related order number, making it easier for you to track of all of the numbers related to an order.

“Use the order number as invoice, shipment and creditmemo number. By default Magento keeps separate counts for order and invoice numbers. This extension ensures that when an invoice, shipment or creditmemo is created it uses the related order number. Magento API Users: Looking at the Magento API documentation this extension could lead to an incompatibility (the API uses the incremental_id instead of the internal unique entity_id to retrieve data). Starting from version 2.0.0 you should use the option System > Configuration > Sales > Order Numbers > Prevent Duplicates=Yes.”

Download from Magento Connect.

Difference between backorder and pre-order

• A backorder is for an item that was in stock previously but is temporarily out of stock.
• A pre-order is for an item that has not been released yet.

Scenario for backorder:

For example, a customer orders 3 items. One item is not in stock. Shouldn’t I be able to Invoice only the 2 items I am shipping now, and then go back in next week and Invoice for the third item when it is back in stock? How do I set this up? – Source: magentocommerce forum

Backorders simply means that the item you are going to order is out of stock and you will receive the item OR the item will be delivered to you when the item will be in stock.

By default, backorder is not enabled in magento. Hence, you cannot add items to cart when the item is out of stock. But, if you enable backorders then you can add item to cart even if it is out of stock.

To enable backorders, go to:

Admin Panel -> System -> Configuration -> Catalog Tab -> Inventory -> Product Stock Options -> Backorders = Allow Qty Below 0 and Notify Customer

Edit Product to Qty = 0 and Stock Availability = In Stock

And backorders are enabled!

When you add the particular product to cart, the product is added to cart and you will see the following message:

* This product is not available in the requested quantity. 1 of the items will be backordered.

You can order the product even if it is out of stock. The product will be delivered to you when it is in stock.