What they are – The accepted way to thank your guests for spending your special day with you and your new spouse.
When do you send them? – As soon as possible after the wedding. You generally have 2 or 3 months as a deadline if your schedule is tight.
Do you need them? – Yes. Every guest needs to receive a thank you card from the bride and groom. A gift is not required to receive these.
Other Tips – It is good form to include a handwritten message in every thank you card. Consider having the envelopes addressed for all confirmed guests before the wedding. Always mention any gifts received by a guest in their thank you card. If a guest gives you a monetary gift don’t mention the amount. Try thanking them for their contribution to your honeymoon, new furniture or whatever else you have decided to purchase with the money you were gifted during your wedding.