Hi,
The sender would need to explain to the courier that they want to claim returned goods relief.
Ask the sender to write ‘Returned goods — relief claimed’ clearly on the package and its accompanying import declaration. The declaration must include a complete and accurate description of the goods, their quantity and value. If you are registered for VAT, make sure your VAT number is quoted on the declaration, CN 22 or CN23.
You can see information about importing goods by post here:
How to claim
Thank you.