When a buyer asks for a quotation the seller should always provide a pro_forma invoice. A pro_forma invoice is an invoice sent in advance of the commercial invoice, which is the final bill that the buyer agrees to pay. Some of the advantages of pro_forma invoice to the importer include to show to his government for foreign currency allocation, opening letters of credit and most importantly, to have a detailed information on the transaction that can help him plan. An accurate and professionally submitted pro forma_invoice can help buyers to make a decision and agree to the quotation.
If you are permitted to submit your invoice via email then it is useful to convert the invoice into PDF format so that it cannot be altered. There is a free PDF creator which you can use at PDFCreator. This creates a PDF file from any application which can then be emailed to the client. Better off, if you can use a software system, it will automatically generate invoice in PFD format, you can also email it straight away from within the a software program.