Unable to Save Item Fulfillment with 3rd Party Billing Due to "The Shipper's Shipper Number Cannot Be Used for the Shipment" Error.

Upon saving an Item Fulfillment, users may receive a notice "The Shippers shipper number cannot be used for the shipment". If the following symptoms concur, consider the succeeding statements below:

• If the Shipping Label integration checkbox is cleared, the Item fulfillment is saved successfully
• User's account number is correct and works outside of NetSuite
• Third Party Billing is used
• Shipping Carrier used is UPS

UPS account number is cancelled. This is the account number registered in NetSuite located at Shipping setup page (Setup > Accounting > Shipping). User's NetSuite account number and  user's UPS account number must both be active to process 3rd party billing.

Contact UPS and verify if the user's UPS Account number is active.