We suggest tracking this type of information in the Mailing Status User Defined Field.

Here are steps to mark an account as Deceased:
  1. Navigate to the account for the Constituent that has passed
  2. Select the Defined Fields link from under the account header
  3. Click Show All Fields from the Tasks box
  4. Click the field Mailing Status under the Base category (it is possible for the field to have been moved to another category)
  5. Mark the box next to Deceased
  6. Click Save And
If you do not have this field set up already, please follow the steps in How to track Mailing Status for your Constituents (BB745089).

Note: Performing these steps will not automatically remove this account from Queries or Reports that you run. In order to exclude those marked with unfavorable Mailing Status values, such as Deceased or No Not Mail, you must use a Clean Mailing List (BB740272).