Grouping only by a month name can combine January from different years. Use a year-aware key or explicit monthly boundaries for transaction reporting.
Choose a real month key
Store the first day of each reporting month as an actual date, such as =DATE(2026,11,1). Display that key with a month-and-year format rather than reducing it to a bare month label.
Confirm that transaction dates are numeric date or timestamp values. Text that looks like a date may not compare correctly with the reporting boundaries.
Use an inclusive start and exclusive end
With transaction timestamps in A2:A100, amounts in B2:B100, and the month key in E2, use =SUMIFS(B2:B100,A2:A100,">="&E2,A2:A100,"<"&(EOMONTH(E2,0)+1)).
The upper boundary is the next month’s start, so timestamps later on the final day remain included. Comparing only with a final-day midnight value can accidentally omit the rest of that day.
Reconcile year boundaries
Test transactions in the same named month across two years, the first instant of a month, and the first instant of the next month. Manually total a small sample and compare it with the result.
Keep time-zone interpretation consistent before assigning timestamps to months. A text label such as Nov 2026 is useful for presentation but should not replace an unambiguous key needed for sorting and matching. Review the source range after adding records, and state whether the report uses calendar months, fiscal periods, or another business calendar rather than assuming those periods are interchangeable.
References
Reviewed against the linked official product guidance on November 3, 2026. Features, limits, screen labels, and access can vary by account, platform, region, and organization policy.