Shipping Item is needed to associate the shipping cost to a posting/General Ledger account. Here are the steps to create Shipping Item.
1. Navigate to Lists > Accounting > Shipping Item > New.
2. Enter the following:
3. On the Shipping Rate tab, set the following:
Select an Account (Shipping)
Flat Rate = Zero
4. Click Save.
When creating transaction such a Sales Order, the Shipping Cost defaults to zero then manually change the amount.