Trying to add rows for missing months for each group

Hi , Anonymous 

According to your description, you want to combine two tables group by [org_id]  and generate the date from 'Organization'[contract_start]  to the Max of  'Date'[Strat of Month]. Right?

You can realize it in Power Query Editor.

Here are the steps you can follow:

(1) This is my test data:

(2)We can add a new Blank Query and we put this in "Advanced Editor" :

let
    Source = Organization,
    Custom1 = Table.AddColumn(Source,"Date",(x)=> List.Select(Date[Start of Month],(y)=> y>=x[contract_start]  )    ),
    #"Removed Columns" = Table.RemoveColumns(Custom1,{"contract_start"}),
    #"Expanded test" = Table.ExpandListColumn(#"Removed Columns", "Date")
in
    #"Expanded test"

 (3)Then we can meet your need , the result is as follows:

For dax , you can create a table and enter this:

Table = 
var _t=CROSSJOIN('Organization','Date')
var _t2=FILTER(_t,[Start of Month]>=[contract_start])
return
SELECTCOLUMNS(_t2,"org_id",[org_id] , "Date" , [Start of Month])

Best Regards,

Aniya Zhang

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