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.
Thank Them, and Ask Them to Thank You _ must be sincere Money is often a touchy subject, so politeness about it is a good idea. Your clients are paying you money that they've earned with blood, sweat and tears, so let them know you appreciate it. You should also invite them to contact you if they have any questions and, more importantly, make it clear that you appreciate their present (and future) business. Some people also welcome testimonials; for example, by adding, "Let us know how we did. Write a testimonial and sent to... " If you're building your website's testimonials page or want to complete the feedback loop, this is a great way to get clients to give feedback on your work. If they have suggestions for making the process smoother, it's also a great opportunity for you to improve.