When shipping charges are defined as Flat Rate, the flat shipping amount is distributed across other matching ship-via lines. For example, UPS charges a flat rate of $10.00 and FedEx charges a flat rate of $15.00. If an order has three lines, the first two are being shipped UPS and the third line is being shipped FedEx, then the first two line items would be charged $5.00 each for shipping and the third line would be charged $15.00 for shipping.
To define shipping charges by a flat rate:
1. On
the Shipping Charges Maintenance
screen, from the Define Shipping Charges task category, click Flat
Rate, as highlighted below.
The Shipping Charges Maintenance – Flat Rate screen displays, as shown
below.

2. Click
Add.
The Define Simple Flat Rate Shipping per Order by Flat Rate table contains
a new row.
3. Select
the effective Begin Date for the
shipping charges from the drop-down.
This shipping method will be charged if the order date is on or after the
begin date.
4. In
Base Ship Amount field, enter
the minimum shipping amount that will be charged regardless of product
weight per order per ship-via.
For example, if an order has three line items, two being shipped via FedEx
and one being shipped via UPS, then the Base Ship Amount defined for the
FedEx will be split between the two lines, AND
the Base Ship Amount for UPS will be applied to the third line.
5. In Amount Charged per Unit Weight field, enter the amount of money charged to every order per unit weight.
6. Select
the effective End Date for the
shipping charges defined from the drop-down.
This shipping method will be charged if the order date is before the End
Date.
7. Click Save.