Hi Julie midgley Midgely
The customs declarations are usually completed by the postal/courier companies on behalf of sender/receiver.
They may ask for information from importer/exporter so they can complete these obligations. You need to check this with the courier company who is handling the package to see what is required.
There are some reliefs available in such circumstances such as returned goods relief or inward processing relief but these need to be claimed when the declarations are made.
You can also claim for repayment if you’ve overpaid import duty and VAT.
More information is available from the guidance at:
How to claim a repayment of import duty and VAT if you've overpaid
Thank you.