This is an interesting, if sometimes thorny question, and the answer isn’t as clear-cut as it might first seem. Below, we’ll cover the basic pros and cons of each approach, and the various ramifications of each choice. Ultimately, it’s your wedding and it’s up to you, but as you’ll see, there’s actually quite a lot to think about.
On The “No, It’s Not Rude” Side
Here, the primary consideration is your budget and the available space. This is your big day. It’s natural that you want all your friends in attendance. In these cases, where you know you only have room for X people, and you’ve got a lot of friends you want to invite that pushes toward the upper limit of the available space, one way to make room for more of the people you absolutely want to attend your big event is to invite them, minus the “+1.”
This isn’t done callously, but rather, pragmatically. Space is limited, and you’d rather have your closest friends by your side than people you hardly know. Given that it’s your big day, your friends will certainly understand your point of view.
On The “Yes, It’s Rude,” Side
On the other hand, we have several centuries of etiquette that tell us that proper form is to assume a +1 for any and all guests you invite. After all, while it’s your big day, the people you’re inviting have personal lives, and they can’t be expected to exclude their significant others to come to your all day event, leaving their spouses, girlfriends, whatevers, out in the cold. Just because it’s your big day doesn’t give you license to forget to be considerate of others.
Also, look at the particular wording of the question. The question presupposes that the person you’re inviting HAS a significant other that you’re intentionally leaving out of the equation. If you have a friend who is single, you enter into a grey area. Given the absence of a significant other, would it be okay in those cases to send the invite to him or her without the requisite +1?
In these cases, the answer is…maybe. Ultimately, what it comes down to here is communication. If you do nothing more than send the invitations out to your single, married, and attached friends, offering no explanation as to the conspicuous absence of the +1, you’re almost guaranteed to get pushback. You’re almost certain to cause hurt feelings.