Sage 50 automatically enters the next sales order number in the SO # field. If you have not yet entered a sales order, this field is blank. Once you enter a sales order number for the first time, Sage 50 increases this number by one for the next sales order. For example, if you first enter a sales order number of 1000, Sage 50 assigns the next sales order the number 1001. This is a required field, and no duplicate sales order numbers are allowed.
If you are using Sage 50 Premium Accounting or higher, you also have the Proposals feature. Proposals share numbers with Sales Orders, meaning that you cannot have a proposal and a sales order with the same number. However, Sage 50 will track proposal numbers and sales order numbers separately so that you can keep sales orders grouped separately from proposals.