SPE16080 - General relief conditions: calculation of Customs debt Goods subject to Authorised Use should have the debt calculated without including any other Union values or goods. For example: brake linings of Commodity Code 8708 3110 are imported at a reduced duty rate. When they are mounted onto the drive axles but not yet built onto the vehicles, a Customs debt is incurred. The debt is only incurred in respect of the brake linings and not the axles petroleum oil is imported for a specific process. Before undergoing that process, it is purified for easier handling. The purification increases the value of the oil by 10%. Before the purified oil is processed, a Customs debt is incurred. The value added to the oil by the purification process is not taken into consideration when calculating the debt