Thanks for your response! I have a few additional questions to ask you about your comment,

"1. Create the parameter and make sure to allow nulls

2. Add an available value as (NULL) either within the query (if using a dataset) or hard-coded" which are:

a. In SSRS how do you make certain that the SSRS report allows for null values?

b. What benefit do I get by allowing NULL to be an available value? How do you specify that NULL is an available value?

c. If I specify NULL as an available value, do I need to specify other values as being available?

d. Just for my knowledge, I would like to know how to specify NULL is an available value in code.