Are you unable to select the previous month in the date parameters for the columns?

Please check that your fiscal year dates in Setup / Settings / Company / Information are correct. If they are not, make a backup before you change the end date. Be aware that any change to the end date will skew your fiscal reporting numbers in Sage50.  EG. If the dates are set to Jan 1 2014 to Dec 31 2014 and the fiscal year is actually Feb 1 2014 to Jan 31 2015, changing the end to Jan 31 will result in a fiscal year of Jan 1 2014 to Jan 31 2015 - 13 months. Or, if you could wait until Dec 31 2014, roll to Jan 1 2015 and then set the fiscal year end to Jan 31 2015. That will result in a 1 month fiscal period, but the next one (Feb 2015 to Jan 2016) will be correct. There is no one right answer; you may want to confer with your accountant on it if this is the problem.