Hi princewmk Kisala,
Trader should speak to customs authorities in the importing county to offer clarification as why re-importing goods incurring customs charges or if they can claim a relief.
As custom charges are imposed by the importing country it is out of our remit to offer advice and we are unable to suggest which system or software traders should use for declarations.
List of customs software providers available on gov.uk.
Software developers providing customs declaration software