Setting Invoice prefix and number enables you to customize your invoice identification and sequence numbers.  This can help cut down on documents that are generated to look like your own invoices and produce something that you can use to identify your store.  This is especially usefu when you are managing more than one shop.  The following tutorial will walk you through setting the invoice prefixes and numbers in PrestaShop 1.5.

Adding Custom Prefixes and Numbers to Invoices in PrestaShop 1.5

1. Login to the Administrator Dashboard as an Administrator
2. Go to the menu bar and hover over ORDERS, then click on the second item that appears in the drop-down menu, INVOICES.  Scroll down into the  PRINT PDF INVOICE options and you will see:
   
   
   
   
   And immediately beneath the INVOICE PREFIX is the INVOICE NUMBER:
   
   
   Note:  If you are using the MULTISHOP option, you will only see the checkboxes on the left when you have selected a specific store.  If you have selected ALL SHOPS or have disabled multishop, then you will not see this box. 
   
   Select the checkbox next to INVOICE PREFIX to activate it.
3. Select a prefix to use and type it into the field next to the INVOICE PREFIX label.  Note that if you have more than one language selected, you will see multiple fields that would be required to be filled - one for each activated language.
   
   
   Example:   INVOICE PREFIX:  MYSTOR
   
                   The invoice number will look like:  MYSTOR000011
4. Click on the checkbox to activate the field for INVOICE NUMBER.  Fill in a number that will identify the next generated invoice.  Invoice numbers will increase sequentially from the number you select.  If you want to use the number currently being used, simply set the number to 0.
5. Select SAVE at the bottom of the page in order to save your entries.

The invoice generated by PRINT PDF INVOICES are identical to the ones that can be generated by the customers.  Here is an example: