ATA carnet procedures: substitute ATA carnets when the original is lost/stolen
If an ATA carnet is lost the holder may ask for substitute carnet. This carnet will take the place of the original carnet - it will not extend the period of validity. The procedures for obtaining a substitute carnet to replace a lost or stolen one are similar to those detailed in ATACPD04450 on replacement carnets. The UK will normally permit the use of substitute carnets.
If a substitute carnet is issued, the carnet holder should forward it to the responsible customs office in the Member State where the goods were first entered to the EU (again, in the UK, this will be the National Carnet Unit (NCU)) who will process and endorse the carnet accordingly and return it to the carnet holder.
Details of the action to be taken by the NCU can be found in ATACPD09350 NCU replacement and substitute carnets
A carnet holder should notify the Customs authority as soon as possible after loss of his carnet. The acceptance of the substitute carnet cancels the lost or stolen carnet.