Sales Order (SO) is a document made by a seller specifying the details about the products/services ordered by a customer, but it hasn't been confirmed yet. So basically it's an offer before a Customer deals with the transaction they want to make.
Sales Invoice is a document made by a seller to specifying the details about the products/services ordered by a customer after they confirmed their orders. So it's a document for a Customer after they willing to confirm their transactions.
For some of the customers, they don't want the sales order and the invoice number to be the same so that they can keep track of the sales order and the invoice easier by differentiating the number of sales orders and invoice. Here is the step to enable the config.
I. Sales Order Configuration
Step 1. Go to Setup, Click More Menu, then Select Module
Step 2. Go to Sell Tab, then Enable Sales Order
On numbering section then change sales order enabled (Yes) then save.
II. Difference between Sales Order & Sales Invoice
Step 1. Go to Sell, then Make Sales Transaction
There are two Numbers on sell menu, Invoice and Sales Order Number. If you park the sales order number will be the number 1 and if you finish the order the invoice number will be the number 2.
Step 2. Recheck Order Number
Here is the park number of the order.
Step 3. Recheck Park Order Number on Invoice Detail
After paying, the park order number will be converted to invoice number.
You might also like to read these articles below:
If you want to see update history customer invoice you can check this article How to see Update History Customer Invoice
If you want to search product and invoice notes in order menu you can check this article Search Product and Invoice Note in Orders Menu
If you want to import sales order via CSV file you can also check this article How to Import Sales Order via CSV File