Why can't cross-border purchase of Watsons goods be invoiced?

Domestic invoices cannot be issued. Every transaction of cross-border goods has to pay customs duties, and they are all foreign goods, so domestic invoices cannot be issued. Only domestic products are purchased, and there are formal invoices. Overseas direct mail products are overseas goods, overseas transactions, and domestic products have no invoices. If the products are stocked in the bonded area, the enterprise will pay them to the bonded area on behalf of the ordering party, and the customs will not issue tax invoices to individuals for a single order.