Ridding this query of Hash Match Join? - sql-server

Question

I have the following query that takes around 26 rows to return 8700 rows of data.
SELECT
R.ClientReferralID,
R.ClientID,
C.FirstName,
C.LastName,
C.FullName,
dbo.fnGetLocalDate(R.ReferralDate) as ReferralDate,
RT.ReferralTypeName,
R.ReferralTypeOther,
RT2.ReferredToName,
R.ReferredToOther,
R.ReferredByID,
U.FullName as ReferredBy,
TS.TimeSpentName,
R.Notes,
L.ReferralLocationID,
L.ReferralLocationName as Location,
R.ReferralLetterSentID,
R.ReferralLetterOnFileID,
dbo.fnGetLocalDate(R.DateCreated) as DateCreated,
U2.FullName as UserCreated,
dbo.fnGetLocalDate(R.DateModified) as DateModified,
U3.FullName as UserModified
FROM
ClientReferral R
INNER JOIN Client C on
R.ClientID = C.ClientID
INNER JOIN LookUp.ReferralType RT on
R.ReferralTypeID = RT.ReferralTypeID
INNER JOIN LookUp.ReferredTo RT2 on
R.ReferredToID = RT2.ReferredToID
INNER JOIN UserAccount U on
R.ReferredByID = U.UserAccountID
INNER JOIN LookUp.TimeSpent TS on
R.TimeSpentID = TS.TimeSpentID
INNER JOIN LookUp.ReferralLocation L on
R.ReferralLocationID = L.ReferralLocationID
INNER JOIN UserAccount U2 on
R.UserCreated = U2.UserAccountID
LEFT JOIN UserAccount U3 on
R.UserModified = U3.UserAccountID
WHERE
(R.ReferralDate >= #StartDate or #StartDate is null) and
(R.ReferralDate <= #EndDate or #EndDate is null)
ORDER BY
R.DateCreated DESC
The execution plan can be viewed here:
https://www.brentozar.com/pastetheplan/?id=B1A5ji7tf
I see the most costly operation is 65% on a Hash Match Join. I was expecting the following index to improve that but no:
CREATE NONCLUSTERED INDEX [Name] ON [dbo].[ClientReferral]
(
[ClientID] ASC
)
Anyone see off hand what I can do here? Please let me know if some sample data is needed.

Answer 1

Try adding an index
ClientReferral ReferralDate
Or
ClientReferral ReferralDate, ClientID
ClientReferral ClientID, ReferralDate

Answer 2

First change
WHERE (R.ReferralDate >= #StartDate or #StartDate is null) and (R.ReferralDate <= #EndDate or #EndDate is null)
To
WHERE R.ReferralDate BETWEEN ISNULL(#StartDate,CAST(0 AS datetime2)) AND ISNULL(#EndDate,CAST(999999 AS datetime2))
After that create an index on
ClientReferral(ReferralDate, ClientID, ReferralTypeID, ReferredToID, ReferredByID, TmeSpentID, ReferralLocationID, UserCreated, UserModified, DateCreated, DateModified) INCLUDE(ClientReferralID, ReferralTypeOther, ReferredToOther, Notes, ReferralLetterSentID, ReferralLetterOnFileID)
Also show the code for
fnGetLocalDate