That is probably due to blank cells, which will evaluate to Jan.

Try something like

=SUM((Range 1<"")*(MONTH(Range 1)=MONTH(A1))*(INVOICE for same Range 1))

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HTH

Bob Phillips

"GeorgeF" wrote in
message ...

I am summing monthly Invoice Amounts from an annual list of occurrences
using an array formula: SUM((MONTH(Range 1)=MONTH(A1)*(INVOICE for same
Range 1)). It works perfectly for every month except January where the
amount is some very large unexplained number. The MONTH (Range 1) is
mmm-dd-yy and the MONTH(A1) is mmm. What is wrong?


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GeorgeF
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