I'll add an Amen to Ron W's statement about putting everything on one page. It is far easier to get specific views (such as a month's or year's data) from a big data source than it is to combine multiple data sources for the "big picture."

So if the boss wants 12 separate pages to view each month individually because it's more human readable, but still wants the YTD figures or annual summary at the end; keep the data in one big sheet and parcel it out to the individual sheets either by VBA or pivot tables.

Depending on the report, you might put all the data in an Excel table and give the boss a slicer and let him pick what months to look at.