DAX function

ENDOFMONTH — DAX function reference

Last day of the month in context.

Syntax

dax

ENDOFMONTH(<dates>)

dax

ENDOFMONTH('Date'[Date])

→ A date

dax

CALCULATE([Total Inventory], ENDOFMONTH('Date'[Date]))

→ Month-end snapshot of an inventory/balance measure

dax

DATEDIFF(TODAY(), ENDOFMONTH('Date'[Date]), DAY)

→ Days remaining until month end

Like FIRSTDATE/LASTDATE, ENDOFMONTH returns a single-row table (the last date of the month), so it’s normally consumed via CALCULATE or coerced to a scalar automatically when a single value is expected.
It's the standard building block for closing-balance measures (inventory, headcount, account balances) because it ignores whichever specific day is selected within the month and always resolves to month-end.

From Time intelligence