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.
Proforma invoices basically contain much of the same information as the formal quotation, and in many cases can be used in place of one. It should give the buyer as much information about the order as possible so arrangements can be made efficiently. The invoices inform the buyer and the appropriate import government authorities details of the future shipment; changes should not be made without the buyer's consent.