How do you write Mr and Mrs in the inside address?

In the inside address of a formal letter, you would typically write "Mr. John Smith and Mrs. Jane Smith" to address both individuals. If you are referring to them collectively, you might write "Mr. and Mrs. Smith." Ensure to include any titles or names as appropriate for the context of the letter. Always use proper punctuation, such as a period after "Mr" and "Mrs" if adhering to American English conventions.