Applied to techShip, SCAC Codes (Standard Carrier Alpha Code) is used to identify carriers (https://en.wikipedia.org/wiki/Standard_Carrier_Alpha_Code).
The SCAC code is used to determine which carrier is used when you import the orders from the WMS, and written back to WMS after you manifest (if supported by the WMS).
Usage varies depending on the technical scenario here's a description of each case.
IMPORTING YOUR CARRIER OPTION FROM THE WMS
When using these, every Carrier profile needs to have a different SCAC code, otherwise, when pulling the information from the WMS (using [Import]), techShip can't determine which one of all to use.
For example, if you have the following carriers:
Stamps / SCAC = USPS
EHub / SCAC = USPSE
By having such setup, techShip is able to determine clearly that some orders are to be processed through Stamps and others through Ehub, even though both will be handled by USPS at the end.
If EHub would also have USPS as the SCAC value, when importing an order with USPS as Carrier, it's not possible to determine through which one it should be imported.
CHOOSING AN EXPLICIT OPTION FROM THE WEB CLIENT
If you are Rate Shopping or importing choosing an explicit carrier from the dropdown, the SCAC value is irrelevant, since you will be overriding whichever value has been assigned in the WMS to arbitrarily use the one you've manually chosen.
OVERRIDING THE CODE FROM THE CLIENT AND BILLING ACCOUNT
When you define a SCAC on the Client/Billing Account level, that SCAC field overrides the one used at the Carrier Baseline level, giving you control to handle this on a Client basis:
1. If you will use [Import] when importing your orders, your SCAC codes must be different between carriers on the Carrier and Client level (Eg. Stamps = USPS, Ehub = USPSE)
2. If you will use Rate Shopping or choosing a specific carrier when importing, your SCAC codes coming from the WMS will be ignored and your manual choice will be used
3. If the Client/Billing Account level SCAC field is left empty, techShip uses the Carrier Baseline level SCAC code
4. You should NEVER have the same SCAC code for different Carrier Baseline accounts (Eg. Stamps = USPS, Ehub = USPS)
NOTE: You can make changes on your Client's Billing Account profiles. Nevertheless, if you require this changes to be made to the source Carrier accounts, reach techShip support with the request.