You can try this. I have corrected the error
CREATE TABLE #OutTable( NetPayable1 DECIMAL, OTAmount1 DECIMAL, NetPayable2 DECIMAL, OTAmount2 DECIMAL)
DECLARE @NetPayable2 AS DECIMAL
DECLARE @OTAmount2 AS DECIMAL
INSERT INTO #OutTable (NetPayable1, OTAmount1)
Select tbl.NetPayable,tbl.OTAmount from (Select sum(cast(S.NetPayable as decimal))as NetPayable,sum (cast(S.OTAmount as decimal)) as OTAmount From tblLocationWiseSalaryRecord S
where month(S.SalarySTDT) = '9' and YEAR(S.SalarySTDT)='2013' and S.CompanyCode='CMP-001' and S.ETCode='ETC-001'and S.DeptCode='DPT-036')as tbl
Select @NetPayable2 = sum(cast(S.NetPayable as decimal)), @OTAmount2 = sum (cast(S.OTAmount as decimal)) From tblLocationWiseSalaryRecord S
where month(S.SalarySTDT) = '9' and YEAR(S.SalarySTDT)='2013' and S.CompanyCode='CMP-002' and S.ETCode='ETC-001'and S.DeptCode='DPT-036'
UPDATE #OutTable SET NetPayable2 = @NetPayable2, OTAmount2 = @OTAmount2
SELECT * FROM #OutTable
DROP TABLE #OutTable