calculate Monthly average based on YTD value

deevs why do you want a column for avg? why this cannot be a measure?

deevs when working with dates, it is a best practice to add a calendar dimension in your model and you can easily create one following my blog post here Create a basic Date table in your data model for Time Intelligence calculations | PeryTUS IT Solutions

Once you have calendar dimension, create a relationship with the transaction table, it will be one to many relationship.

Add the following two measures

Avg Numerator = 
VAR __current = MIN ( CALCULATE ( MAX ( 'Calendar'[Date] ), ALLSELECTED ( 'Calendar' ), VALUES ( 'Calendar'[Year] ) ), TODAY() ) 
VAR __startOfMonth = EOMONTH ( __current, -1 ) + 1
VAR __endOfMonth = EOMONTH ( __current, 0 )
VAR __daysUntilToday = CALCULATE ( COUNTROWS ( 'Calendar' ), DATESBETWEEN ( 'Calendar'[Date], __startOfMonth, __current ) )
VAR __dayUntilEOM = CALCULATE ( COUNTROWS ( 'Calendar' ), DATESBETWEEN ( 'Calendar'[Date], __startOfMonth, __endOfMonth ) )
VAR __avgNumerator =  MONTH ( __current ) - 1 + ( DIVIDE ( __daysUntilToday, __dayUntilEOM ) )
RETURN __avgNumerator

Average = 
VAR __actual = CALCULATE ( SUM ( 'Table'[Actual] ), ALLSELECTED ( 'Calendar' ), VALUES ( 'Calendar'[Year] ) ) 
RETURN
DIVIDE ( __actual, [Avg Numerator] )

To visualize the data, use the month column from the Calendar table and above measures, and that will do it.

deevs from which table you are using month in your visual?

deevs you are not answering my question. My question is from which table you are using Month in your visuals. If you please read my question and reply, it will help otherwise there is no point going back and forth.

deevs something is missing here, share the measures you added to the model, make sure you added these as measures, not columns. also share the relationship image between the calendar table and the transaction table.