Count expression SSRS Report

=SUM(IIf(Fields!Doc_Type.Value = "Shipments", 1, 0), "YourDataSetName")

this worked for me with no errors. saw this on another post.

You can do this a couple of ways:

SUM(IIF(Fields!accepted.Value="Y",1,0))

or

COUNT(IIF(Fields!accepted.Value="Y",1,Nothing))

COUNT is a count of all Rows, so even by returning 0 it will get included in the count. This is why returning Nothing should do the trick.