Susan Jones and husband John
It depends on the project instructions or the surname field help (purple circle with question mark). Usually in my batch experiences the field help will indicate to mark it <BLANK> - but I believe I have also seen where it does read 'if husband and wife are listed with one of them including surname ... Include that surname for both.'
So it really just depends on the instructions - but field help should indicate.1
From General Indexing Guidelines:
How to Index Individuals Whose Names Were Not Fully Recorded
- If the record provides the given names of a husband and wife followed by a single surname, such as "John and Mary Smith," index Smith in the Surname field for both records. However, if a document does not indicate a shared surname, such as "John Smith and Mary" or "John Smith and Mary, his wife," do not assume the wife's surname from the surname of the husband.