Our products offer two main choices of calculation method for your shipping rates: fixed fee or calculated. Fixed fees (either a flat dollar amount or a fixed fee code) are set by you per item; calculated fees are calculated by our shipping engine, based on carrier rates, and determined by item weight/dimensions and origin-destination.

Fixed Fee Codes are a powerful way to use fixed fees.  You can use them simply to configure your fixed fees in your account, rather than in your item HTML (this is a "non-associated" code).  You can also configure a fixed code that is linked to different rates for one or more carrier services, offering your customer a choice of fixed rates depending on the shipping service they prefer. We call this an "associated fixed rate" as it is associated in the cart with the name of one or more shipping services.  You can also define a fixed fee code differentially based on geography, i.e., one rate for domestic destinations and another for international.

You may mix together flat fixed fees, fixed fee codes, and calculated rates for your items as you see fit.  Allowing for this versatility means we have made some decisions on the appropriate functionality for the way rates are generated depending on the mix.  Below is a summary  of our logic:

Flat Fixed Fee and Fixed Fee Code Items Together:

• Flat Fixed Item and Fixed Fee Code (non-associated) Item:  fixed amounts are added together.
• Flat Fixed Item and Fixed Fee Code (associated) Item:  fixed amounts are added to each associated service rate.
• Fixed Fee Code (non-associated) Item and Fixed Fee Code (associated) Item: Fixed amount is added to each associated service rate. 
• Multiple Fixed Fee Code (associated) Items: in this case , the behavior depends on whether the associated services "intersect":
  • Intersection:  combined rates for intersecting services are shown;
  • No Intersection:  A "fixed" service is shown in the cart, combining the rates for the least expensive associated service for each code.

Calculated and Fixed Fee Items Together:

• Calculated and Flat Fixed Items:  The fixed dollar amount value of the fixed item/s is added to each calculated rate.
• Calculated and Fixed Fee Code (non-associated) Items: fixed dollar amount is added to each calculated rate.
• Calculated and (one or more) Associated Fixed Fee Code Items (services intersect):  The combination rate is shown for the intersecting services.
• Calculated and (one or more) Associated Fixed Fee Code Items (no service intersection):  The rate for the Fixed Fee Code is added to each of the calculated rates. If the code is linked to more than one service, the rate for the least expensive service is used.
• If an Associated Fixed Fee Code item is added to a "mixed service" rate (which results when items from various origins do not support any shared servcies), the associated service definitions are ignored (while maintaining the geographic definitions).