Dates in accounting are vitally important. If your business is using the accrual method of accounting, your sales invoices will not be included in income until the date the entire order has been shipped to the customer. So, if a customer, for example ordered three items and two were shipped say 03/20xx that sales invoice will not show up in your sales income until the final item has been shipped out to the customer say 12/20xx, to properly account for the goods by the accrual method. Something to keep in mind with this method is that you will not be reporting as much sales tax and will be paying less excise and b & o taxes, since you are paying only for the sales taxes on the invoices that are closed and completely shipped to customers.