Documentary commercial bills of exchange drawn upon firms or banks where documents are for payment cannot be discounted upon the market, as in the case of such bills where documents are for acceptance, for the reason that banks abroad to which bills are sent for collection will not undertake to discount commercial bills unless they are what is called "clean" bills - that is, those having no documents or those which permit the documents to be delivered when the draft is accepted by the drawee.

A documentary or commercial bill of exchange, accompanied by instructions from the exporter or drawer, to deliver documents (bill of lading, etc.) only upon payment of the draft by the importer or drawee, which are drawn upon a firm, are subject to a discount rate of 1 per cent. below the Bank of England official minimum discount rate. If the instructions are to deliver documents upon acceptance of the draft, the same rate of discount by the holder (bank) at 1/4 of 1 Per cent. above the private discount rate of the day.