When giving a gift, it's the thought that counts -- but what if you don't give a gift at all? It's simple, really: If you don't get an invitation, etiquette does not require you to give a gift, according to a Divine Caroline article titled "Gracious Giving: Seven Rules of Wedding-Gift Etiquette."
Gifts are Voluntary
The arrival of a wedding invitation carries with it the implication that you will give the happy couple a gift. Sometimes, however, you may not be invited to the actual ceremony, but a reception only. Or you may hear that a co-worker is getting married, but you never receive an invitation. In such cases, you are not expected to give a gift -- but many do anyway. It usually depends on the situation. For example, couples that have families separated by a great distance will often hold a wedding in one location and then a reception a few weeks later in the other location. If you weren't invited to the wedding because of the distance, you might choose to bring a gift to the reception.