Compare Two list and sum values based on all matching values and by month

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in C10

=SUMIFS(Data!$E$2:$E$34,Data!$A$2:$A$34,Summary!C$8,Data!$D$2:$D$34,Summary!$A10)

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I interpreted a little differently. I understood you want to include all the items in Summary!$A:$A and include even if they are only part of the strings in Data!$D:$D

And since you want to also include any additions (automatically?) they are referenced by a dynamic range $A$10:INDEX($A:$A,MATCH("zzzz",$A:$A)) embedded in the formula. It's a bit awkward so I would recommend saving that bit as a dynamic named range (DNR) in Name Manager and reference it by name in your final formula(s).

Try this in the meantime.

Formula:

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With that DNR as Element_Names this formula is shorter.

Formula:

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