Incremental increase in date in formula

You could use formula:

Formula:

=SUMIFS('Dividend Income'!$D:$D,'Dividend Income'!$A:$A,">="&DATEVALUE("1-"&$B3&"-"&C$2),'Dividend Income'!$A:$A,"<="&EOMONTH(DATEVALUE("1-"&$B3&"-"&C$2),0))

in C3, then copy across and down.

Better still, you could use a pivot table...