Since July 1st 2021, the rules on EU VAT have changed.
Specifically around sales that take place through marketplace channels like eBay and Amazon, but also about the information that needs to be passed to couriers to ensure that the end customer does not pay EU VAT when the parcel is delivered.
You can see our blog posts around this on the StoreFeeder blog page:
This specific error is because the order in question that you are trying to despatch has had the EU VAT collected by the marketplace and we need to include their IOSS number in the information that we send to the courier when we create the label.
This error is usually because you are using a Royal Mail service that is not IOSS compatible.
Since February/March 2021, Royal Mail has been advising senders to switch international services to one or more of their "core services" which will handle IOSS orders.
If you are seeing this error it is because you are trying to despatch using a Royal Mail service that is not one of the Core services.
Here are the Royal Mail core services:
More information can also be found here - https://www.royalmail.com/business/international/guide/delivered-duties-paid/ioss-faqs
If you get this error, you need to go into 'Settings > Shipping Configuration > Shipping Methods' and update the service codes on your international shipping methods.
You can find more information on shipping methods here - https://support.storefeeder.com/hc/en-gb/articles/360007739497--Creating-A-Shipping-Method