It's perfectly acceptable to decline a wedding invitation, provided you use the proper etiquette. Promptly notify the couple of your regrets with the RSVP card, and send a wedding card to wish the couple your best and explain your reason for missing the celebration. Although you don't technically have to do so, it's a warm gesture to also send a gift and plan to get together after the wedding.
RSVP and Wedding Card
When you decide you won't attend a wedding, the first order of business is to let the couple know in a timely manner. Mark the RSVP card appropriately and send it back. You can also add a brief note on the RSVP, such as, "Sorry to miss it!" Once you return the RSVP, buy a wedding card to share your best wishes and explain why you can't attend. For example, write that you're out of town for a work engagement, but that you'll be thinking of the couple on their special day.
Give a Gift
Although you don't technically have to give a gift when you don't attend the wedding, giving something is a sign that you're happy for the couple and are celebrating with them in spirit. Remember, you were important enough for the couple to invite to their nuptials, so responding with a gift shows that you value the couple, too. One option is to buy something off the gift registry, but you can also get anything you'd like. If you aren't able to get a gift by the time of the wedding, aim to do so by the time the couple returns from the honeymoon.
Honor Your Commitment
If you've sent back a wedding RSVP saying that you plan to attend, do your best to follow through on this commitment. Although certain factors beyond your control can prevent you from attending, wedding website The Knot reports that it's poor etiquette to change your mind once you've confirmed your attendance. As soon as you realize you aren't able to attend, call the couple, explain the reason and apologize for the inconvenience. However, always do your best to honor your initial commitment of attending.
Plan to Get Together
It's proper etiquette to follow up with the newly married couple shortly after the wedding and arrange to get together. Ask the couple out to brunch or have them over for coffee to ask about their big day and their happiest memories. Ask to see wedding photos, hear the details of their honeymoon and relive the moment together. Taking this approach shows that you value the couple's friendship and are indeed interested in their wedding, even if you weren't able to attend.