There are two ways to ship orders using a Third party account:

1. You can add a Billing account at the Client level an set up Third party account there. For example, please see the following solution

2. You can enable checkbox "Enable TPL Billing Override " on the client level. In this case, you should have carrier account numbers and carrier postal codes in orders in WMS system, you need to enable this checkbox for clients where you need to use third-party billing.
(see the solution here )

If you have enabled the option above and you get the error "Hard 9120078 - Missing bill receiver account number" that means the order you are trying to ship does not contain the Third party account number and postal code in WMS. You can add a Third party account on order level.

To add Third party account on order level, you need to know all 3 columns to copy to these fields (see the screenshot below). All 3 is mandatory in case of UPS, so you need to fill out all 3 fields.