You can address it to only one, or address it to both using both names. Either way is acceptable.
The correct way to address an envelope to a married couple that have different last names is to use both of their names. For example, you could write Mr. Johnson and Miss or Ms. Dwyer.
You can address a letter Dear Fred and Bertha (or whatever the actual names are). Personally, I often address my letter Dear Folks. That way there won't be any dispute about why I put Fred's name before Bertha's.
No, do not sent separate thank you notes and address the envelope and put both names of the married couple on the top of the card to thank them for the volunteering they did.
Unmarrie couple both name on deeds the mortgage is on his name
no because if something happens then it happens to both of you.
If you are addressing a married couple who are both doctors you can address them two ways. You can address them by either stating Drs. Jack and Jill Smith or Dr. Jack Smith and Dr. Jill Smith.
I would say The Reverands John and Mary Smith.
It depends on the state. Some states, such as New York, allow for a gay or lesbian couple to have both names on the birth certificate. Others do not.
Try "Doctors Judy and John Jorgenson" or something like that, where the names are correct. If you aren't using first names, you could try doctor and doctor Jorgenson, although it is a bit more awkward. Alternatively, you could try "Doctors Jorgenson."
You can address a letter to two doctors as: Drs. John & Jane Doe.
The name on the account. If both names are on the account, both are fully liable for the debt.