Monthly totals are in nearly every report. The reliable way is SUMIFS with a start date and an end date. It does not need a helper column and it works on any date range.
Set up the month list
In F2 type the first day of the first month, for example 01-Jan-2026. In F3 use =EDATE(F2,1) and copy down. Format the cells as mmm-yyyy.
The formula
Dates in column A and sales in column C. In G2:
=SUMIFS($C$2:$C$1000, $A$2:$A$1000, ">="&F2, $A$2:$A$1000, "<="&EOMONTH(F2,0))
It adds every sale from the first day of the month to the last day of that month.
Add another condition
To total one region only, add one more pair: , $B$2:$B$1000, "North".
Why this beats SUMIF with TEXT
Some people compare TEXT(date,"mmm") with the month name. It mixes up the same month from different years. A date range avoids that mistake.
Avoid the end-of-month time trap
If your dates contain a time of day, a sale at 5 pm on the last day is larger than the date itself and gets missed. In that case use "<"&EDATE(F2,1) (less than the first day of the next month) instead.
Pivot table alternative
A pivot table can group dates by month in two clicks. Use SUMIFS when you need a fixed layout, such as a monthly summary table that feeds a chart.