Month on Month Comparison based on another value

Hi jamesholland198 

I think your Month column is text type, you may need to build a Month table as below.

Unrelated Month Table:

Then add a YearMonth column in your sample table.

YearMonth =
VAR _MonthName =
    LEFT ( 'Table'[Month], 3 )
VAR _MonthNum =
    CALCULATE (
        SUM ( 'Month'[MonthNumber] ),
        FILTER ( 'Month', 'Month'[Month] = _MonthName )
    )
VAR _YearNum =
    FORMAT ( RIGHT ( 'Table'[Month], 2 ), "General Number" ) + 2000
RETURN
    _YearNum * 100 + _MonthNum

Build the billing in previous month column by YearMonth column.

Billing in Previous Month = 
VAR _PreviousMonth =
    MAXX (
        FILTER (
            'Table',
            'Table'[SageRef] = EARLIER ( 'Table'[SageRef] )
                && 'Table'[YearMonth] < EARLIER ( 'Table'[YearMonth] )
        ),
        'Table'[YearMonth]
    )
RETURN
    CALCULATE (
        SUM ( 'Table'[Billing] ),
        FILTER (
            'Table',
            'Table'[SageRef] = EARLIER ( 'Table'[SageRef] )
                && 'Table'[YearMonth] = _PreviousMonth
        )
    )

Result is as below.

Best Regards,

Rico Zhou

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