When your friends or family pool their money to purchase a gift, it allows them to give something that would be out of the price range of any individual. Naturally, you're grateful and need to write a proper thank you note to the individuals. The correct etiquette for a group gift varies, based on the circumstances.
In a case where a small group of people got together to buy you a gift, the proper etiquette is to send each person her own thank you note. Couples or families can receive a single note. For example, if the group that contributed to the gift consisted of your parents, your unmarried brother and your sister who is married with children, you would send one card addressed to both parents, one to your brother, and one addressed to your sister's family.
When more than 10 people contribute to the gift, it's sometimes appropriate to write a single thank you note and post it in a location where all the members of the group can see it. For example, if the entire office chipped in on a baby shower gift, you might write a nice letter and post it in the break room.
Without a Central Location
Sometimes, there's no central location for you to post a thank you, and you'll have to write several thank you notes. Use your judgment to decide how to thank people. If the group gift came from co-workers in different offices, for example, you could send group thank you notes to each office. However, if all of your sorority sisters -- who now live across the country -- went in on a gift, you'll want to send a separate note to each one.
What to Write
Make your thank you card as personal as you can. Thank the individual for his contribution to the gift. If the present was money or a gift card, try to specify how you will spend the money. For example, you might say, "Thank you for contributing to the office pool to buy me a gift card for my baby shower. My partner and I will be using this generous gift to purchase a new crib set for the baby." If you know who was responsible for coordinating the group gift, it's important to give that person a little extra thanks.