Use this checkbox on client level to enable third-party billing. Because for many wms/clients third party account # may contain garbage, it is disabled by default.
If you already have carrier accounts and carrier postal in orders in WMS system, you need to enable this checkbox for clients where you need to use third-party billing. If it is enabled but do not work, please provide example order number to Techdinamics support: https://support.techdinamics.com
Also, please note, the shipper (shipper account # - this is entity who ships) is responsible for address validation, and any address correction fees or other fines will be charged to Shipper, not to the Third party.