Combine and sum 6 sheets into one sheet or report

I have 6 sheets all set up the exact same way:

1 category column + 12 columns for the months of the year

each sheet represents a different company

how can I combine (sum) the cells from each of the 6 sheets into one sheet or report?

ie: create a new report that sums the cells in row "expenses" , column " July" for all 6 sheets

I thought adding the 6 sheets into one report would do it, but it does not sum the cells, it displays the first sheet data only.

Answers