ATA carnet procedures: format of the ATA carnet: transit vouchers and counterfoils
On occasion, the ATA carnet will contain transit documentation. This will meet the requirements of some contracting parties who require goods moving through their territory, or moving within it, to be covered by transit.
The EU does not require goods to move under transit unless the goods are moving through the EU on their way to a final destination outside the EU, for example Australia - UK - USA.
It is highly unlikely that you will be presented with transit documentation but where this does arise, see ATACPD05400.