When should you send a thank you note for a gift received? As soon as possible. Up to two weeks is considered the acceptable time frame (wedding gifts fall under a different guideline), but why wait? You either write it now, or a week from now. The longer you wait, the feeling you had when you opened the gift will be farther from your mind. A late thank you note might also convey to the giver that you were not that excited or appreciative for their gift. A handwritten note is your way of showing gratitude for the time and money they spent.
Certain occasions require a handwritten note: when you have been a houseguest; when you receive a gift (this includes someone taking you to dinner and other acts of giving); when you are the honored guest at a party (wedding shower, for example); after a job interview. I think it is nice when every person has a set of personalized notecards, along with a couple’s card, as part of their stationery wardrobe.