As we are sent out in past, If payment term is L/C and customer need to declare sample in shipping documents, we need to declare the sample into application L/C.
Also if invoice, packing list show the sample so in B/L need to show as well because avoid the discrepancy with bank.
All shipping documents need to match.
Another way to avoid the troubles and complicated, We will put the sample innermost of container and not declare in any documents.
But if you need invoice, we can issue invoice as picture below and sent you by e-mail.