Beginner help with finding the difference between two tables

Hi RD6308 ,

Since you did not give a specific table, I had to create my own table for testing according to your description, please point out if there are any problems.

Please try below steps:

1.below is my test table 

Budget: "Index" column are used to sort the "Month" column by this column

Transcations:

Model:

2. create a measure and add it to table visual

Budget VS Actuals =
VAR cur_month =
    SELECTEDVALUE ( Budget[Month] )
VAR cur_budget =
    CALCULATE ( MAX ( Budget[Amount] ), Budget[Month] = cur_month )
VAR cur_actuals =
    CALCULATE ( MAX ( Transcations[Amount] ), Transcations[Date] = cur_month )
VAR diff = cur_actuals - cur_budget
RETURN
    IF ( diff > 0, "+" & diff, "-" & diff )

Please refer attached  .pbix file 

Best regards,
Community Support Team_ Binbin Yu
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