Taking into account first day of the month.

I have been trying to do a monthly summarization of invoice records.  When selecting the month, Ninox omits the first day transactions i.e 01/01/2021  or  03/01/2021 etc. I have created a field which draws the Month out of the entry date field from the table.

let x := 'Dept';
sum((select 'Inovices Entry Table' where Month = 2 and 'Dept = x).'Total')

Any help would be appreciated.