report critera = null or empty

report critera = null or empty

I am trying to report all open or non-completed.

I also have some records that were created before I added the completed field so they are empty or null until I we complete them.

I can't seem to find the null function tried "isnull", "" , " " 

Thanks for any advise.

report criteria looks like this

completed is equal to "No"

or

completed is equal to ""