Third-party billing is a ShipStation feature that allows you to charge a shipment's label to a third-party account (that is, a postage account not connected to ShipStation). You may want to use this feature if you have an agreement with the shipment's recipient, or another third-party, that they will pay for the billing fees.
You will need the third party's postage account number and postal code to configure third-party shipping in ShipStation.
ShipStation will send the billing details to the selected carrier and the carrier will then bill the correct account.
If this is something you will do regularly, consider using Automation Rules to automatically apply third-party billing to your orders. Be sure the rule first sets the shipping service and package type correctly, then adds the third-party account details!
The Recipient and Third-Party designations are for information and reporting purposes only. Either option will tell the carrier to charge the entered account.
The third-party account must be approved by the carrier for third-party billing. If you receive an error when attempting to create a label with third-party billing, check with the account owner to ensure the carrier has approved the account for third-party billing.