Copy and paste entire column value into another column based on current month or not

GokilaRaviraj , Try using below m-code

let
// Load your data source
Source = Excel.CurrentWorkbook(){[Name="YourTableName"]}[Content],

// Add a column with the current month name
AddCurrentMonth = Table.AddColumn(Source, "CurrentMonth", each Date.ToText(DateTime.LocalNow(), "MMMM"), type text),

// Duplicate the "Other income" column
DuplicateOtherIncome = Table.AddColumn(AddCurrentMonth, "CurrentMonthData", each [Other income]),

// Add a conditional column to copy data based on the current month
AddConditionalColumn = Table.AddColumn(DuplicateOtherIncome, "UpdatedColumn", each if [CurrentMonth] = "September" then [CurrentMonthData] else null),

// Remove unnecessary columns
RemoveColumns = Table.RemoveColumns(AddConditionalColumn,{"CurrentMonth", "CurrentMonthData"}),

// Rename the updated column to the current month name
RenameColumn = Table.RenameColumns(RemoveColumns, {{"UpdatedColumn", Date.ToText(DateTime.LocalNow(), "MMMM")}})
in
RenameColumn