Dear …
Thank you so much for __(becoming a member of / your donation of -($amount)- to)__ __(Name of Organization)__. Your support means a great deal to the volunteers, staff and more than __(#)__ (type of animals)__ in our care at the animal shelter. By __(making this donation/purchasing an annual membership)__, you help us to __(briefly describe type of project/provide continued aid for…)__.
As you may already know, on average we receive __(#)__ newly rescued animals into our shelter on a monthly basis. The feeding and care of so many animals requires our ongoing attention. So when financial supporters like you show us that you understand these needs, we are humbled by your commitment. You make a big difference in our ability to meet the needs of __(describe what needs you are meeting)__.
We are pleased to enclose your receipt for income tax purposes and again we extend our sincere thanks to you, __(Name)__, for your __(continued/generous/etc.)__ support.
Sincerely,