Sql query with where clause

Hello,
I have a sql query need to add a where clause.

DECLARE @Last_Friday AS DATE = '2017-02-07'
DECLARE @This_Friday as date = '2017-02-17'

SELECT GuestName, ArrivalDate, 
       CASE
              WHEN Extendedto IS NULL THEN DepartureDate
              ELSE Extendedto
       END AS DepartureDate
FROM CORRESPONDENCE
WHERE (ArrivalDate >= '2016-01-01'
       AND (
              (Extendedto IS NULL AND DepartureDate >= @Last_Friday)
              OR Extendedto >= @Last_Friday
              )
       AND (ArrivalDate >= @Last_Friday AND ArrivalDate <  @This_Friday)
    OR (ArrivalDate < @Last_Friday 
              AND (
                     (Extendedto IS NULL AND DepartureDate >= @This_Friday)
                     OR Extendedto >= @This_Friday
                     )
              )
       )

Select allOpen in new window

Where clause to be added is :

WHERE ( DeleteRecord is null or DeleteRecord = 0)'