Hi Canapone,

Interesting approach - just a couple of comments.

1. Each instance of those options will effectively call the SUMIF(s) function 31 times, so will probably be slower to calculate than the single SUMIFS or even the SUMPRODUCT option.

2. Using "ROW($1:$31)" is not robust, meaning if you insert rows at row 1 of the worksheet the formula will no longer work as intended. This can be dealt with, but given the first comment I'd probably stick with one of the other options.

FWIW - I over did the date coercion and my suggestion can be reduced to:

=SUMIFS(B:B,A:A,">="&D3&C3,A:A,"<="&EOMONTH(D3&C3,0))