Negociable, porque, si la empresa exportadora que ha soportado un determinado importe de derechos de aduana no tiene nada que comprar al importador, vende su crédito aduanero en el mercado de la bolsa o en un banco.
Secondly, it is negotiable, because if the exporting company, which has paid duty, has nothing to buy from the importer, it can sell its customs credit on the stock market or to a bank.