SQL: Last Day Of Month

For any date go back a month, then add a month to it.

SELECT  [dtMonthLastDay] = DATEADD(MONTH, DATEDIFF(MONTH, -1, GETDATE()), -1)  

Last day for any month etc. by Pinal Dave

----Last Day of Previous Month
SELECT DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE()),0))
LastDay_PreviousMonth
----Last Day of Current Month
SELECT DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE())+1,0))
LastDay_CurrentMonth
----Last Day of Next Month
SELECT DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE())+2,0))
LastDay_NextMonth