One question we are often asked is who should formally be thanked after a funeral. It is important to note that the answer to this, as with most other things in Jewish tradition, often varies.
It is most common to write thank-you notes for donations or contributions that were made in a person’s memory, or to people who may have sent food to the family. It is also common to thank anyone who was exceptionally helpful in organizing shiva, etc. It is not expected that you should write a note to thank every person who attended the funeral.
However, in the more observant community it is NOT expected that thank-you notes be written, as that community views helping with shiva or making contributions in someone’s memory something that is a mitzvah – a commandment, not just a good deed – and, therefore, does not require thanks. Another part of the reasoning is they feel that grieving families should do just that – focus on their grief and not have to spend their time obligated to the duty of writing thank-you notes.