When writing a letter of invitation for lunch, it should be kept simple and include all of the necessary information. The writer should use a tone that matches the occasion. For example, business lunches should use professional language, fonts and stationery, while a casual get together among friends may require nothing more than an email.
Lunch invitations should include the menu or items being served. Additionally, it should include all of the pertinent information for contacting the host, finding the restaurant and the time of the get-together. The invitation should always indicate the dress code for the establishment or occasion, and let the invitees know that the host would appreciate acceptance or regrets as soon as possible.