Letter of Invitation. Registration must be completed and paid in full before a Letter of Invitation may be requested.During registration select the checkbox labeled "I would like a visa invitation letter". Invitation letters will be created for each individual and emailed. Please fill out the Letter of Invitation form in its entirety. We will review your request and follow up with you as soon as possible. Are you prepared to start your journey of professional development? Explore interesting Dallas conferences in 2025 with invitation letter that are listed below. An invitation letter can be issued in support of your visa application after you have completed your registration for The ASTA Travel Advisor Conference 2024. The 2025 Annual Road Profile Users' Group (RPUG) conference will be held in Dallas, TX from April 28 – May 1, 2025.