DAX Code for Distinct Count of Records with Blank Payment Date and "SW...

Below is the DAX Code for your requirement:

/// 

/// Returns a distinct count measure for records where the payment date is blank.
/// 
///  Input table for the measure.
/// Column on which we are applying distinct count
/// Payment date column name which we need to check if it is blank or not
/// Source column which we need to compare against "SWIPE"
/// A new measure.
/// The function will fail if the provided column or table is not found in the model.

Distinct_NoPayDate_Swipe = 
CALCULATE(
    DISTINCTCOUNT('MPOS ACCR Detail'[Mem HH ID]),
    FILTER('MPOS ACCR Detail',
        ISBLANK('MPOS ACCR Detail'[Payment Date]) && 'MPOS ACCR Detail'[MPOS Source] = "SWIPE")
)

The above code works as follows - CALCULATE evaluates the DISTINCTCOUNT('MPOS ACCR Detail'[Mem HH ID]) measure applied to the 'MPOS ACCR Detail' table after filtering it based on two conditions specified. The FILTER function returns the requested column where the [Payment Date] column is blank, and the [MPOS Source] column equals "SWIPE".

Code Usage Example:

This code snippet could be handy in scenarios where we want to analyze the behavior of customers who did the "SWIPE" but haven't given the payment details yet. This can be used to focus on this particular customer segment for the follow-ups. You can use this measure with many visualizations throughout Power BI like tables, cards, line charts, bar charts, etc. depending upon other measures you are plotting together with this.