Error when calculating Returning Customers

Hi EllieSiroco1 

Please try this:

Here I create a set of sample:

Then add a calculated column:

Returning Customers =
VAR CurrentPeriodStart =
    DATE ( 2024, 11, 01 )
VAR CurrentPeriodEnd =
    DATE ( 2024, 12, 31 )
VAR _previousSales2 =
    CALCULATE (
        SUM ( 'orders-web2019'[Sales inc VAT] ),
        FILTER (
            ALLSELECTED ( 'orders-web2019' ),
            'orders-web2019'[customer email] = EARLIER ( 'orders-web2019'[customer email] )
                && YEAR ( 'orders-web2019'[Order date] )
                    = YEAR ( EARLIER ( 'orders-web2019'[Order date] ) ) - 1
                && MONTH ( 'orders-web2019'[Order date] )
                    = MONTH ( EARLIER ( 'orders-web2019'[Order date] ) )
        )
    )
RETURN
    IF (
        'orders-web2019'[Order date] >= CurrentPeriodStart
            && 'orders-web2019'[Order date] <= CurrentPeriodEnd,
        IF (
            _previousSales2 > 0
                && 'orders-web2019'[Sales inc VAT] > 0,
            "Returning",
            "New"
        )
    )

The result is as follow:

Best Regards

Zhengdong Xu
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EllieSiroco1 

Sorry I think I misunderstood you before.

I think this simply solution will do what you you want ...

Create 4 measures ... 

Has NovDec2023 sales = 
// create a temp file of dates in range 
VAR mydates =  FILTER('Calendar', 'Calendar'[Date] >= DATE(2023,11,01) && 'Calendar'[Date] <= DATE(2023,12,31))
RETURN
// return 1 if there were any sales within date range
CALCULATE(
INT(NOT(ISEMPTY(Sales))),
mydates
)

Has NovDec2024 sales = 
// create a temp file of dates in range 
VAR mydates =  FILTER('Calendar', 'Calendar'[Date] >= DATE(2024,11,01) && 'Calendar'[Date] <= DATE(2024,12,31))
RETURN
// return 1 if there were any sales within date range
CALCULATE(
INT(NOT(ISEMPTY(Sales))),
mydates
)

New customers = 
// create temp file of qualifiying customers  
var mysubset =
FILTER(VALUES(Sales[CustomerKey]), 
    [Has NovDec2023 sales] = 0 &&
    [Has NovDec2024 sales] = 1)
 RETURN
 // count the rows
 COUNTROWS(mysubset)  

Returning customer = 
// create temp file of qualifiying customers  
var mysubset =
FILTER(VALUES(Sales[CustomerKey]), 
    [Has NovDec2023 sales] = 1 &&
    [Has NovDec2024 sales] = 1)
 RETURN
 // count the rows
 COUNTROWS(mysubset)   

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