Sending thank you cards to donors is important as it makes the donor feel individually recognized and increases the chances the person will donate again. Send these out very shortly after you receive the donation, no longer than two days after. This speedy delivery shows how efficient your organization is and also how much you want to tell the donor thank you.
Use a personal, but professional tone when writing the letter. You don't want the donor to feel like it is a letter from the government, rigid and impersonal, but you don't want him to feel like he just gave a donation to a company that is not professional. Write in a tone that resembles the way you would talk to your boss on the first day of work, personal but professional.
The format of the letter is similar to the format of a business letter. Each new paragraph goes on a new line and a line is skipped in between. No indentations are used. Start with the date, then the donor's address on another line, then your salutation and the message. You can use the same letter for every donor, but make it personal by changing the name of the donor in each letter so she feels like it was written to her, not like she was sent a mass mail-out.
Every organization chooses their content differently. Some like to talk about how much money was raised, whereas others feel like that is bragging. One way to get around this is to state that your organization met its fundraising goal at the benefit and if it was exceeded or not. A brief recap of where the funds are going is another option to include in the content. Also, talk briefly about how the benefit went overall. Keep it short. One brief paragraph thanking the donor and another telling how the fundraiser went and how the funds are allocated is all that is needed.
The layout for the thank you card should be simple. Ornate cards with bells and whistles may make the donor wonder about where his donation is really going. If you can use artwork from your organization, put that on the front of the card with a simple thank you, and the message inside. An example of this kind of artwork is if your organization works with kids, then put a picture of one of their drawings on the front of the card.