When it comes to an invitation letter for a visa, it typically does not have to be handwritten. This post contains a guide to writing your own Invitation Letter for Immigration and a sample Affidavit of Support and Guarantee for visiting relatives abroad.Writing a letter is one of the best ways to invite other people to a particular event. You can use and download these invitation letters in word format. You should include the name of the host, formal expression, the event purpose, date, time, and venue, contact details, and RSVP. In this article, we detail when to use a formal letter format, the different types of formal letters and how to write your own. An invitation letter should have three parts: Sponsor information (the person who is writing the letter) Nonimmigrant information. No invitation letter is needed if the purpose of the activity is to sightsee and visit in the United States. Permission to Enroll in Another Institution.