What should the letter say? Make sure you have a valid F1 or J1 Visa, a current form I-20, and that your passport is valid for at least another six months.You will need a CAS to submit your Student visa application. On this page we will explain how you can apply for your CAS with the University of Suffolk. Toronto Notary Public offers a sample Letter of Invitation and Aolemn Affirmation for a visitor visa to Canada. 1. Your invitation letter explains your status in the US, what you are doing, and whom you are inviting. You will need to complete the online application form. Fresh, high-quality milk delivered right to your doorstep.