How to include 1's on the seating chart?

Have they RSVP'd back confirming a plus one with no name?

Yes. FH called his cousin yesterday because he didn't mail his RSVP in. His response was 'I'll bring someone with me. I just dont know who that will be yet'.

You could put John smith and guest. Or just his name and then just have the seat avaliable.

I told those people that I needed to know the name by XX date (one day before final numbers were due) or we would not have a meal for that person. I don't know the true etiquette for this situation though so this maybe should not have been the answer.

I'd probably do "Guest of "

Put guest for now. About a week before the wedding, tell them you need a name for the escort card.

While it is considered polite to obtain the guests name, if he wont give it to you, I would go with guest of John Smith.

We had a few guests with plus ones and they were contacted a few days before our final headcount, to make sure they were still bringing someone and confirm the names. On the seating chart, I put "Billy's plus 1" when I didn't know the name yet,

If they won't give you a name then "and guest" will have to work

I've been that awkward +1 before and my escort card just said "last name of person I was with- guest".

I put on my RSVP for them to list the name because I was genuinely worried about this issue. I'm hoping it all works about when my invites go out next month