Getting previous month and previous data

Hello,

I am using 2008 SSRS I have a subscription report. On the first of every month I am able to get the previous month data for my report, which send it to a file on the first of every month. The code I am using for the month parameter is Month(Now() -1, I am having trouble with the code for the year I can ask for current year, but When January 1st comes around I want to get December of 2015. When February 1st 2016 comes around I want January 2016 data, etc. If I set the Year parameter for current year I won't get December 2015. Any help will be appreciated on coding. Thank you.