Maiden name                                                                     Ms. Jane Smith  

                                                                                             Miss Jane Smith (Usually Miss is for girls under 18)          

Married, keeping maiden name                                          Ms. Jane Smith

Married, uses husband's name socially                              Mrs. John Wilson

                                                                                            Mrs. Jane Wilson (Nowadays this is acceptable

                                                                                            Ms. Jane Wilson

Separated, not divorced                                                      Mrs. John Wilson

                                                                                            Mrs. Jane Wilson

                                                                                            Ms. Jane Wilson

Divorced                                                                              Mrs. Jane Wilson

                                                                                            Ms. Jane Wilson

                                                                                            Ms. Jane Smith (maiden name)

Widowed                                                                             Mrs. John Wilson*

                                                                   *If you don't know the widow's preference, this is the traditional and preferred form

                                                                                            Mrs. Jane Wilson

                                                                                            Ms. Jane Wilson

Married, she uses her husband's name socially                 Mr. and Mrs. John Wilson
NOTE: Traditionally, a man's name preceded a woman's on an envelope address, and his first and surname were not separated (Jane and John Wilson). Nowadays, the order of the names—whether his name or hers comes first—does not matter and either way is acceptable. The exception is when one member of the couple 'outranks' the other—the one with the higher rank is always listed first.
Married, she prefers Ms.                                                    Mr. John Wilson and Ms. Jane Wilson
                                                                                           Ms. Jane Wilson and Mr. John Wilson

*Do not link Ms. to the husband's name:  Mr. and Ms. John Wilson is incorrect
Married, informal address                                                   Jane and John Wilson
                                                                                           John and Jane Wilson
Married, she uses maiden name                                        Mr. John Wilson and Ms. Jane Smith
                                                                                           Ms. Jane Smith and Mr. John Wilson
                                                                                           If you can't fit the names on one line:
                                                                                           Mr. John Wilson
                                                                                           and Ms. Jane Smith
                                                                                           *Note the indent, either name may be used first
Unmarried, living together                                                  Mr. John Wilson & Ms. Jane Smith 
                                                                                           Note: Use one line
A woman who outranks her husband:
Elected office, military rank                                                The Honorable Jane Wilson and Mr. John Wilson
                                                                                           If you can't fit both names on one line (note indent):

                                                                                           The Honorable Jane Wilson
                                                                                           and Mr. John Wilson
Professional or educational degree                                     Dr. Jane Wilson and Mr. John Wilson
Both are doctors (PhD or medical) and use the same last name
The Doctors Wilson (omit first names)                                 Drs. Jane and John Wilson / Drs. John and Jane Wilson
                                                                                             Dr. John Wilson and Dr. Jane Wilson / Dr. Jane Wilson and Dr. John Wilson
Both are doctors (PhD or medical), she uses her

maiden name                                                                        Dr. Jane Smith and Dr. John Wilson
                                                                                              Dr. John Wilson and Dr. Jane Smith

Woman                                                                                             Ms. is the default form of address, unless you know positively

                                                                                                         that a woman wishes to be addressed as Mrs.
Professional designations—use only for business                           Jane Wilson, CPA
Note: Do not use Ms. or Mr. if using a professional designation

Socially, drop the professional designation and use Mr., Ms., or Mrs.: Ms. Jane Wilson
Attorneys and some court officials                                                     Jane Wilson, Esquire
Note: If using Esquire, do not use Ms. or Mr. In conversation or socially, 'Esquire' is not used; use Mr. or Ms.: Ms. Jane Wilson
Attorney at Law                                                                                  Ms. Jane Wilson
                                                                                                            Attorney at Law
This is an alternative to 'Esquire' for attorneys. Use Mr. or Ms. and use two lines with no indent

Addressing a Woman your paragraph here.

Addressing a Couple

Invitations By Joan

Envelope Addressing