Negative sales by customer

DAX DAX Calculations
2

Hi @ericdao,

First. Thanks for a clear description of your requirement and providing a PBIX :+1:

Your model didn’t include a Date table, I’ve added one but please review the relevant content added below as to why it is important to include that in your model.

Next I created this measure:

Negative Sales by Customer v2 = 
SUMX( 
    SUMMARIZE( Sales, Sales[Customer ID], Dates[Date] ),
    IF( [Total Sales] <0, [Total Sales], BLANK() )
)

with this result.
image

.
I hope this is helpful. Here’s your PBIX.
Negative sales.pbix (86.9 KB)