Do I have to use titles like "Mr." and "Mrs." on wedding invitations?

For formal weddings, titles are expected. For casual celebrations they are optional, so match the choice to your overall tone.

• Formal: use titles such as Mr., Mrs., Ms., and Dr. on outer envelopes.
• Casual: first and last names only is perfectly fine.
• Keep the addressing style consistent with the invitation's tone.
• When unsure, lean toward the more formal option. Guests never mind the extra respect.