Cumulative Value based on condition

Hi, eryka_90 

You can try the following dax to achieve your need.

Measure:

Net Due = 
VAR _netDue =
    CALCULATE (
        COUNTROWS ( 'Table' ),
        FILTER (
            'Table',
            MONTH ( 'Table'[Net Due Date] ) - 1
                = MONTH ( SELECTEDVALUE ( 'Date'[firstDayofMonth] ) )
        )
    )
RETURN
    _netDue

0-15 = 
CALCULATE (
    COUNTROWS ( 'Table' ),
    FILTER (
        'Table',
        'Table'[DaysDiff_1] <= 15
            && MONTH ( 'Table'[Net Due Date] )
                = MONTH ( SELECTEDVALUE ( 'Date'[firstDayofMonth] ) )
    )
)

16-31 = 
CALCULATE (
    COUNTROWS ( 'Table' ),
    FILTER (
        'Table',
        'Table'[DaysDiff_1] < 31
            && 'Table'[DaysDiff_1] > 16
            && MONTH ( 'Table'[Net Due Date] )
                = MONTH ( SELECTEDVALUE ( 'Date'[firstDayofMonth] ) )
    )
)

DaysDiff_1 = 
VAR _netDueDate =
    SELECTEDVALUE ( 'Table'[Net Due Date] )
VAR _lastDayofMonth =
    EOMONTH ( _netDueDate, 0 )
VAR _dayDiff =
    INT ( _lastDayofMonth - _netDueDate )
RETURN
    _dayDiff

DaysDiff_2 = 
VAR _netDueDate =
    SELECTEDVALUE ( 'Table'[Net Due Date] )
VAR _lastDayofMonth =
    EOMONTH ( _netDueDate, 1 )
VAR _dayDiff =
    INT ( _lastDayofMonth - _netDueDate )
RETURN
    _dayDiff

Best Regards,
Yang
Community Support Team

If there is any post helps, then please consider Accept it as the solution to help the other members find it more quickly.
If I misunderstand your needs or you still have problems on it, please feel free to let us know. Thanks a lot!

How to get your questions answered quickly --  How to provide sample data in the Power BI Forum