Setting Up Third-Party Carrier Account

You have the ability to extend the option to use your customer's UPS account. This is set on the Account level, and will automatically apply to all orders using UPS shipping that run through that account. 

This is done under Configuration > Third-party billing. 

You also have the option to charge a fee for this service, since you no longer have an opportunity to have a profit on shipping. 

This is done on the Price sheet assigned to the account under Shipping and handing > Handing > Third-party billing shipment charge.