An International Import Certificates (IIC) is an end use assurance. If a company or individual in the United Kingdom is intending to import controlled goods from another COCOM (Co-Coordinating Committee on Multilateral Export Controls) member country it is the norm to apply for an International Import certificate at the request of the Licensing Authority of the country of export.
An IIC constitutes an undertaking by the importer to import the goods into the country of destination, without diversion or transhipment elsewhere, and not to re-export the goods without an export licence from the Licensing Authority in the country of importation. It is also an assurance from the Government of that country that it will control any subsequent export of those goods.
If you are importing controlled goods into the UK, you will need an Interntional Import Certificate and the purpose of the certificate is to reduce the risk of strategic goods being diverted.