Addressing wedding invitations and save-the-dates is typically done in the same fashion. Although not required, most traditional invitations consist of an inner envelope and an outer envelope. Your save-the-dates should be addressed in the same manner as your outer envelope which is addressed and stamped with the full names of the adults invited.
Placing an "and" between their names signifies the union. For example "Mr. and Mrs. John Sullivan."
Traditionally, the husband's title goes first, unless his wife happens to have a professional title, in which case she should be addressed before him.
Finally, when addressing a married couple, you should always address both members of the married couple, even though the couple may only know one or knows that only one will attend.
Their names should be placed on separate lines and listed alphabetically.
For same sex couples, names should also be organized alphabetically, even if they are married and share a last name, unless one of them has a professional title.
Children over the age of thirteen should receive their own wedding invitation.
Young brothers and sisters can be sent a joint invitation.
If you prefer not to send separate invitations to children, make sure that their names are written on a line below their parents' names on the inner envelope and organized from oldest to youngest. You do not need to list their names on the outer envelope.
No abbreviations with the exception of non-professional titles (Mr., Mrs., Jr., etc.) should be used when addressing names on the envelopes. Avoid using the title Ms. As it is often used in business. Middle names should also be spelled out completely. Professional titles such as Doctor should be spelled out and Avoid using symbols for the word "and."
The inner envelope only has the names of those who are invited to the wedding. For example, the inner envelope of a married couple is addressed "Mr. and Mrs. Sullivan", with neither the first names nor the address appearing on the envelope. The inner envelope also allows you to be very specific as to who is invited to the wedding. It is a great way to communicate to your friend whether she or he is welcome to bring a guest.
When a guest is invited but his or her name is unknown, it is proper etiquette to only address the outer envelope to your friend "Miss Kennedy" and address the inner envelope to your friend and her guest "Miss Kennedy and Guest". If the inner envelope is addressed to only "Miss Kennedy", it should be clear to your friend that she should not bring a guest. For your close friends and family, it is entirely acceptable to address the inner envelope in informal or familial terms. This is a great way to add a personal touch to your invitation.
All house numbers are written in numeric form except for "one," which is spelled out. Apartment, suite, and zip codes are written in numeric form. Avoid using state abbreviations.
Cities, states and numbered streets are written out in full (with the exception of D.C.). Avoid abbreviating the common words like "Street," "Boulevard," "Avenue." The only optional abbreviations are for Saint (St.) or Mount (Mt.), which can be written either way.
Return addresses should be printed on the back flap of the envelope and be centered and in the same color ink that you are using for the wedding invitation. Name or names are excluded from the return address.
Married Couples (same last name)
Outer envelope: Mr. and Mrs. Dean Davis
Inner envelope: Mr. and Mrs. Davis or Dean and Allison
Married Couples (different last names)
Outer envelope (maiden name): Mr. Dean Davis and Mrs. Allison Smith
Outer envelope (hyphenated name): Mrs. Allison Smith-Forrester and Mr. Dean Davis
Married Couples (with professional titles)
Outer envelope (male professional): Doctor and Mrs. John Jones
Inner envelope: Dr. and Mrs. Jones
Outer envelope (male judge): The Honorable and Mrs. Mark Darcy
Inner envelope: Judge and Mrs. Darcy
Outer envelope (female married judge): The Honorable Elizabeth Darcy and Mr. Mark Darcy
Inner Envelope: Judge and Mr. Darcy
Outer envelope (male officer): Colonel and Mrs. Bruce Reynolds
Outer envelope (female officer): Lieutenant Bella Wayne, US Navy and Mr. Ryan Wayne
Outer envelope (both professionals): Doctors John and Bridget Jones
Outer envelope (two professionals different professions): Doctor John Jones and Reverend Bridget Jones
Married Couple with children
Outer envelope: Mr. and Mrs. Sullivan
Inner envelope: James and Sarah
Susie, Johnny, and Meg (list by age, oldest first)
Unmarried Couples (listed alphabetically)
Outer envelope (if they live together): Miss Bridget Jones
Mr. James Sullivan
Inner envelope: Miss Jones
Outer envelope (if live separately): Miss Bridget Jones (send to closest friend)
Inner envelope: Miss Jones
Unmarried Single Guest
Outer envelope: Miss Bridget Jones
Inner envelope: Miss Jones or Bridget (if close friend) and guest