this way...
SELECT vEmpCode,SiteCode,ToDate,FromDate,Day(FromDate) As FDays ,Month(FromDate) As FromMonth,
Year(FromDate)As FromYear
FROM Employee_Site_Tag
Where [SiteCode]='SIT003' AND [vEmpCode]='101407'
AND
MONTH(FromDate)<=
(
CASE WHEN Year(FromDate) < 2013 THEN 12 else case when Year(FromDate) = 2013 THEN 1 else 0 end END
)
and (( Month(ToDate) >= 1 and Year(ToDate) >= 2013 ) OR Todate IS NULL )
Happy Coding!
:)