What shipping cost should be listed on a custom invoice?

[JPcollection]

Hi All,

When we send item oversea we need to fill in a custom / commerical invoice for the clearance, there is a section "shipping cost" in the template given by my shipping provider. But I am using flat rate for my shopify shipment so the actual shipping cost on order details (i.e. customer paid) may not align with the actual shipping cost (I pay to the carrier).  Which shipping cost should I fill in the custom/ commerical invoice?

Thanks.

[3DMak]

I need to know the answer to this too.  This is embarrassing when sending a custom invoice to a customer and the shipping costs are wrong.