The following is a list of instructions on how to write a commercial invoice.
If your institution does not have a standard form invoice you can write one up on your institutions letterhead.
1 - On letterhead from your institution, title your letter Commercial Invoice.
2 - Write your institutions import business number on the letter.
3 - Create a list of the goods you plan to ship, showing the quantity of each item, the country of origin for that item, and the dollar value of the goods. Country of origin is the country where the goods were made.
4 - Tally up the value of all the goods in your list and write the total dollar value at the bottom of your list. State which currency you are using, for example state the value shown is in Canadian dollars, US dollars, Euros, or which ever currency is most convenient for you.
5 - Make a brief statement as to why the goods are being sent to the destination. For example, to be used in an experiment and will subsequently be returned to the originating institution on a particular date.
6 - In bold print write the following statement, Your country Customs Clearance to be done by Your company Ltd.
7 - Sign your letter.
8 - Send us a copy of your commercial invoice and attach 3 copies to your shipping documents when you ship the goods.
*Please see Aussie's replies below*