No, an invitation letter is not mandatory, but it is strongly recommended when applying for a U.S. B-1 Business Visa. The letter should come from the US-based company or organization you plan to visit and must outline:
- The purpose of your visit (e.g., meetings, conferences, negotiations)
- Dates and duration of your stay
- Details of the host company and your relationship with them
- A statement confirming that you won’t be engaging in paid employment
- Including an invitation letter strengthens your application by proving the legitimacy and intent of your business trip.