amount of customs duties

You should note that Customs duty liabilities (the amount of customs duties legally due) will not be discharged if the sterling amount received by Customs after conversion is less than the amount legally due.

Lastly, I should like to mention the difficulties giving rise to the failure to collect the considerable amounts of customs duties and other taxes arising from TIR operations, which are attributable to ineffective implementation of existing mechanisms and a lack of monitoring of transit operations.