Apple Numbers IF rules with checkboxes
A look at SUMIFS and SUMIF in the help files will point you in the right direction.

First case:

Total all currency in column when checkbox is not ticked.  A checkbox not ticked returns false, whereas ticked is true.  The column headers are named in the example table so the formula in the screenshot reflects those names in the place of the column letter designations.

Formula: =SUMIF(A, false, G) 



Second case:

Total by month.  The trick is to get a valid date value.  The formula below is a starting point.
Formula for June in the example below: =SUMIFS($Currency,$Date,"&gt;=2018/"&amp;MONTH(D7)&amp;"/01",$Date,"&lt;=2018/"&amp;MONTH(D7)&amp;"/30")

For details on the SUMIFS function, see the help documents.



NOTE: the Month 'June' is actually a date 2018/6/1 formatted as month name in this example.  One could substitute the current month this way: MONTH(NOW) but note that the formula will change each time the file is opened.  So if opened in July, that will be reflected in the formula. See the This month total in the example below.



Sample Table