If you'll want to get more than just January's data, I'd strongly
recommend using a Pivot Table, which can organize information by month,
quarter, week, etc. See

http://peltiertech.com/Excel/Pivots/pivotstart.htm

Otherwise, you can use

=SUMPRODUCT(--(MONTH(A3:A38)=1),C3:C38)


In article ,
"JC" wrote:

I have columns of data with the date entered in column A
in format MM/DD/YYYY. Column C contains cost data.

I am trying to sum up data to the side by month. The
formula I tried using is =SUMIF(A3:A38,"MONTH(A3:A38)
=1",C3:C38)and =SUMIF(A3:A38,MONTH(A3:A38)=1,C3:C38.

Neither method is evaluating the data correctly. Any
assistance would be appreciated.