Here’s a couple of ideas.
First there’s this one.
This may not solve the month cut off issue but it will certainly give you some ideas.
I think what you’ll ultimately want to do it create a calculated column which would enable you to place an additional filter on your results.
Something like this
Financial Record =
VAR CurrentMonthYear = CALCULATE( SELECTEDVALUE( Dates[MonthnYear] ), Dates[Date] = TODAY() )
IF( Dates[MonthnYear] < CurrentMonthYear, TRUE, FALSE )
This just gives you a way to create that additional filter that can be added to some logic in your formula.
See how you go with this idea.