I need to calculate the previous month in SSRS based off a month parameter. If the user enters June 2024, it will calculate May 2024. The trouble comes when I need to calculate January to December.
=CDate(Format(DateAdd("m",-1,Parameters!Month.Value),"MMM"))
I am assuming you are passing the whole date in the parameter:
Parameters!Month.Value = 1/1/2024
=MonthName(MONTH(DATEADD("M", -1,Parameters!Month.Value)))
This will give you the value December