You should use
SUM() aggregate function[
^]:
SELECT WH.date,PN.partyname,SUM(RA.recamount),(DE.totalweight*DE.rateperkg)as totalAmount, (DE.totalweight*DE.rateperkg)-RA.recamount) as dueamount
FROM K_RT_WarehouseDetails WH
inner join K_RT_Dailyentryretail DE on WH.sno=DE.branchdate
inner join K_RT_AmountReceived RA on RA.partyname=DE.partyname
inner join K_RT_PartyName PN on DE.partyname=PN.sno
GROUP BY WH.date, PN.partyname
ORDER BY WH.date, PN.partyname