Shouldn't there be a comma in there?
Select EmpId,Name,(BUSON_SALARYSTR.BASICSALARY / dbo.GetNoofDaysPerMonth(@Month, @Year)) *
(dbo.GetNoofDaysPerMonth(@Month, @Year) - dbo.NoofdaysAbsent(EmpId,@Month,@Year))(convert(decimal, '12343.5787') as BASICSALARY ,BUSON_SALARYSTR.CODE FROM BUSON_EMP
INNER JOIN BUSON_SALARYSTR ON BUSON_SALARYSTR.CODE = BUSON_EMP.SalaryStructure
Select EmpId,Name,(...) * (...)(convert(decimal, '12343.5787') as ...