Numbers and Numbers and Records and Books _ must be trackable Referring to "invoice #9048," rather than "That invoice I sent you last month, I think on a Tuesday," is much easier to track for both you and your client. Assign numbers to your invoices systematically, consistently and chronologically. Some people number their invoices by year (for example, 2009043 would be the 43rd invoice of 2009). You could also specify a code for the project. For example, ABC06 would be the 6th invoice for the ABC project that you're currently working on. Having an invoice and project numbering system keeps everything in line.
About proforma invoice _ A Proforma invoice is an invoice provided by a supplier in advance of providing the goods or service. A quotation in the form of an invoice prepared by the seller that details items which would appear on a commercial invoice if an order results. It is more of a customs declaration form used in international trade that describes the parties involved in the shipping transaction, the goods being transported, and the value of the goods. It is the primary document to declare value for customs. It is not a true invoice, because the seller does not record a pro forma invoice as an accounts receivable and the buyer does not record a pro forma invoice as an accounts payable.