If you are sending IOSS shipments with Whistl  from Shiptheory, use the following guide to make sure your IOSS numbers are being transferred to Whistl correctly to avoid double taxation and other import/export issues when shipping into the EU.


Step 1: Setup your IOSS number in Shiptheory


Before any IOSS shipments can be created with Whistl, make sure you have set up either your sales channel or your Shiptheory account so that Shiptheory has the correct IOSS number to send to Whistl. For more information on which sales channels pass the IOSS number to Shiptheory and how to handle the situation for channels that do not, see our IOSS Setup Guide here.


Step 2: Use the correct Whistl services for IOSS


Not all Whistl services support IOSS shipments. Only the following international services support IOSS. If you do not have access to these Whistl, you may need to speak with your Whistl account manager to have them enabled.


  • International Insight Flat
  • International Insight Packet
  • International Standard DDP Packet
  • International Standard DDP Small Parcel
  • International Standard DDP Parcel


When using the above services and formats the shipment will be flagged as an IOSS shipment regardless of the shipment value and if a valid IOSS number exists on the shipment (see step 1 above).


It is your responsibility to check that your Shipments are being sent as IOSS shipments


If you have any questions about IOSS, or if you would like to check your Shiptheory setup, please feel free to reach out to support.