I'm in SSRS 2008 R2. I have a matrix that has two parameters - one is the year and the other is customer. The customer parameter is multi-value. My report has six columns per month. Three columns come directly from my query and three are expressions with data from my query. When I pick a single customer in my parameter, everything works fine. When I pick all customers or multiple customers, I get errors only on the expression columns. The error is when a customer doesn't have data for the month. So if Customer A has data for Jan, Feb, Mar but Customer B has data for only Feb and Mar, the non-expression columns are blank but the expression columns in Jan for Customer B is Customer A data. I've tried to add an if statement using IsNothing to the expressions, but it doesn't make a difference. Thought I had it in the wrong sequence so changed that and still nothing. I hope this all makes sense. I'm not an IT person so any help would be appreciated. Thanks

I figured it out. I had to change my query to include all months/periods for each customer even if nothing was reported/available.