How To Write A Declaration Letter For Customs . Make sure you use transparent tape (or put it in the plastic envelope attached to the package) so that the form can be clearly read. This is not for sales and therefore, does not have any commercial value. Customs Officer Cover Letter Example from www.icover.org.uk Keep your paragraphs and sentences short and stick to. This shipment contains diagnostic specimens packed in accordance with iata packing instruction 650. Do make your concerns known objectively.